Identifying and Managing Sycamore Blight on Sycamore Trees

Identifying and Managing Sycamore Blight on Sycamore Trees

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

Do you want the good news of the bad news first? The bad news is that many of our area sycamores are infected with sycamore blight this spring.  The good news is that sycamore blight seldom kills a tree.  Well, it's good news for those of you who like sycamore trees.  Most of you know that sycamores are not my favorite type of tree.  One reason that sycamores don't hold my esteem is that they get sycamore anthracnose .

Sycamore anthracnose, also know as sycamore "blight", is a fungus disease which commonly attacks the leaves and twigs of sycamore trees.  The cool, wet weather this spring has been ideal for the development of this disease.  The fungus survives the winter in cankers (which look like small wounds) on the branch twigs and also on fallen leaves and twigs.  During cool (55 degrees Fahrenheit), wet spring weather, the spores of the fungus develop in these cankers.  The spores are blown and splashed by the rain onto newly expanding buds, shoots, and leaves. The spores germinate and the fungus infects and kills plant tissue.

The first symptom of sycamore blight is usually sudden browning and death of single leaves or clusters of leaves as they're expanding in the spring. It’s easily mistaken for frost or wind injury.

A quick look around the area, and you’ll easily find a large number of sycamore trees that are quite sparse and appear to be leafing out very slowly.  Many of these are affected by “blight.”  As our weather turns warmer (hopefully), the trees will form new leaves but the foliage will not be as dense as in other years.

If our cool and wet weather persists, later leaf infections may also occur.  Symptoms of these later infections appear as brown dead spots which start at the base of the leaf or at avein on the leaf.  The brown spots then follow the veins outward.

Control of anthracnose on susceptible trees is difficult, mainly because of the large size ofmost sycamores.  Recommended cultural control consists pruning off and destroying infected twigs and dead branches and also raking up and disposing of all the fallen leaves and dead twigs.  Both of these actions are designed to remove the organism that lives through the winter and produces spores the next spring.

Spraying with a fungicide to protect expanding buds and leaves from the fungus can be done in the spring as the buds begin to swell andjust start to break open.  This is most practical where trees are young and small enough for you to be able to achieve good coverage when spraying.  Adequate coverage is difficult to achieve on large trees, even for competent applicators with good equipment.  Recommended fungicides are applied at bud‑break and then again at ten to fourteen day intervals during periods of wet weather. Remember that good coverage is essential for effective control.

I should note that sycamore and plane trees vary in their susceptibility to the disease.  Oriental plane trees are resistant while native sycamores are not.  There are some cultivated varieties of Oriental hybrids that are known to be resistant to the disease.  These varieties are "Bloodgood," "Columbia," and "Liberty."   If you must plant a sycamore, plant one of these resistant varieties.

Locust Borer Attacks Black Locust Trees

Locust Borer Attacks Black Locust Trees

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

The locust borer (Megacyllene robiniae) only attacks black locust trees.  It’s a native insect and was first found in the eastern part of the United States in natural stands of black locust trees.  The locust borer caused problems in colonial times by rendering the durable black locust wood unsuitable for use as fenceposts.  As settlers moved west in the country, they brought black locust trees... and the borer with them.  The borer is now found throughout North America.

The adult locust borer is one of the “long-horned beetles” with antennae almost as long as its body.  This 3/4 inch black, slender, elongated beetle is sometimes mistaken for a wasp because of the distinctive bright yellow markings on its back.  Most characteristic is the “W” shaped band across the wings.  The legs are reddish.

As an adult beetle, this pest feeds on goldenrod and other flowers in late summer and early fall.  After feasting on flowers and mating, the female adult beetles lay eggs singly or in small groups in bark crevices, cracks, callus tissue around wounds, and other hiding places on the bark of black locust trees.  Interestingly, this egg laying activity usually takes place from early afternoon to late evening.

In about a week, the eggs hatch into tiny larvae which bore directly into the bark until they reach living tissue.  They spend the winter in the inner bark where they make a small hibernation burrow about one inch in length.  In the spring, they start feeding on the tree in earnest, boring upward and inward towards the center of the trunk.  At some point they make a sharp turn and descend about 3 inches down the trunk within the heartwood.  

They’re apparently good housekeepers, pushing frass and sawdust out of their entrance holes and other openings made for clearing out clogged tunnels.  In the spring, visible clues to their presence are moist areas on the bark, which is caused by sap coming from these opening.  The frass and sawdust materials pushed out of the tunnels and collecting beneath the trees is also a good clue.  They continue boring until the tunnels are three to four inches long and about 1/4 inch in diameter.  The tunnel is oval-shaped to accommodate their round head and the way it eats the wood.  It’s such a good eater, you can actually hear it feeding as it chomps away on the wood.

In mid-summer, the larvae, which have grown to approximately one inch in length, are ready to pupate... the stage where they change from a larva into an adult.  They emerge about a month later as adult beetles.  They exit through the openings they made as larvae.  There is one generation per year.

This past week I have been receiving samples and calls from numerous tree owners and cities in the region who are concerned about the damage from the borer that they’re finding in their black locust trees.  The city of Kahlotus has a great number of infested trees and the city of Richland is faced with the predicament of having 600 to 800 black locusts within their entire park system, with 60 or more in Howard Amon Park alone.  A number of these are badly infested and will probably need to be removed for safety reasons.

What type of actual damage does the borer do?  The beetles primarily attack the trunks and branches of black locust (Robinia psuedoacacia) trees, which are 1½ inches in diameter up to seven to eight inches in diameter, occasionally attacking larger wood.  It usually waits to attack trees until they’re four years of age or older.  Heavy attacks by the locust borer will weaken trees and retard growth.  Severe infestations or repeated attacks can leave wood virtually “honeycombed” and prone to limb breakage during windstorms.  During our last windstorm, a number of badly infested trees lost limbs and branches.

The borer tends to attack stressed trees more heavily.  The first line of defense against this pest is to keep the trees in as good health as possible with adequate watering and fertilization practices.  Usually older trees are not attacked, but when there is a high population of borers or the trees are stressed, the tops of older trees become infested too. 

While the locust borer doesn’t generally kill trees, trees can be killed when the population becomes epidemic in proportion.  Drought weakened trees are especially susceptible to attack.  Soil compaction also contributes to borer attack.  Even pruning creates favorable sites for infestation, since the adult females like to lay their eggs in callus tissue on the edge of wounds.

When the borer is already in the wood there isn’t much one can do in the way of “control” other than pruning out badly infested wood.  Chemicals applied to the bark will not penetrate and kill the larvae.  Systemics applied to the roots for uptake into the plants also don’t get into heartwood and older sapwood tissues where the larva does most of its feeding. 

Any chemical insecticides used for control are applications made to trunks and main branches to prevent reinfestation by young borers in the fall.  Appropriate applications of pesticides labeled for borer control are made in late summer or early fall.  Sprays are targeted at the bark of the trunk and larger branches (greater than one inch in diameter).  The spray applications should thoroughly wet the bark surface.  Special attention should be given to wounds and callus growth where the borers like to lay their eggs.

Heavily infested trees with dying tops serve as “brood” trees for the borer.  It would be advantageous to remove these trees from an area where other, healthier black locusts are growing.  However, the trees should be removed and destroyed during the dormant season when they contain the larvae.  Limbs and branches should also be removed if an attack leaves their wood structurally weak.  These should be removed as soon as the hazard is detected.  When replacing these trees, a community should consider planting a mix of species.  Pure stands or large groups of any one species invites devastation by an insect population or an attack by disease, like the locust borer or Dutch elm disease. 

One of the law’s of nature is “the survival of the fittest.”  This certainly applies to black locust trees.  Trees that are healthy and not stressed will survive; weakened trees will probably end up being dinner for the locust borer and candidates for the chainsaw.  

Fruit Trees Can be a Nightmare for Tri-Cities Gardeners

Fruit Trees Can be a Nightmare for Tri-Cities Gardeners

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

It=s a nice dream.... being able to grow fruit right in your own backyard.  However, this dream often turns into a nightmare for many home gardeners who are not aware of how much work it can take to grow acceptable quality worm-free fruit.  It requires regular sprays of insecticides to keep apple and cherry fruit free of worms.  Even if you tire of spraying and are willing to sacrifice your fruit to the Aworms@, residents of Benton and Franklin counties are required by law to control the wormy pests on apples, crab apple, hawthorn, and cherries.   The obstacles to growing backyard fruit trees often leads to many questions from would-be backyard orchardists when they discover that their dreams aren=t easily realized.  Here are some of their frequently asked questions... and answers.

Why do Benton and Franklin counties require me to spray my apple and cherry trees?  Backyard fruit trees, where codling moth and cherry fruit fly are not controlled, serve as a source of infestation for commercial orchards.  Infestations of codling moth and cherry fruit fly in nearby backyard trees mean a grower will have to use more insecticides or additional pest management strategies to control these pests in his orchard.  This leads to increased costs and an increase in the amount of pesticides used.  The infestation may also lead to infested fruit within his crop, which could mean the grower will get less money for his crop or it may even mean he can=t sell it at all.  Because commercial tree fruit production is a significant part of our local agricultural economy, it=s important to keep backyard fruit trees from becoming a liability to commercial growers.

How difficult is it to control these pests? Both codling moth and cherry fruit fly require regular sprays, generally every 7 to 10 days, during the growing season to keep the fruit Aworm free@.

Spraying trees is time consuming ... you have to mix the sprays, apply them, and clean up afterwards including laundering your clothing.  You also need the right equipment for spraying.  If the trees are large, you=ll need more than a hose-end or garden sprayer to reach the tops of large fruit trees.  It=s unsafe to spray fruit trees using a ladder.  You also should wear protective goggles, long sleeves, long trousers, a hat, and shoes when applying pesticides to your trees. These items must be laundered separately from other laundry right after spraying.

The weather can definitely make it difficult to apply the regular sprays needed to keep pests in check.  You should not spray when the temperature is expected to go below 40 degrees when applying dormant oils and you should not spray when the daytime temperature is above 85 degrees when applying sulfur or petroleum-based sprays. Wind can lead to the spray drifting off target, so you should never spray when there=s any noticeable wind.

If I apply a dormant spray, won=t that take care of the wormy pests?  No.  The dormant fruit tree sprays that are applied in the late winter just as buds start to swell are aimed at controlling diseases, not insects.  Dormant oils which should be applied just before the buds open in the spring, only help control certain insects that overwinter on the bark of the tree, such as aphids, scale, and mites.  The dormant oils have no affect on codling moth or cherry fruit flies.

I don=t like using so much pesticide.  Is there any organic way to control these pests?  Some organic sprays are available for codling moth and cherry fruit fly control, but most don=t provide adequate control to keep the home orchard worm-free and most would also require more frequent application.  Codling moth can be controlled without sprays, if you are willing to thin and bag all the apples on a tree using special paper bags. 

I=ve heard about the use of pheromones (insect hormones ) to control codling moth in apple orchards.  Wouldn’t that also work for a backyard orchardist like me?  The lures impregnated with insect sex pheromones are useful tools in codling moth management in large orchards.  The lures are placed around the perimeter of an orchard to confuse male moths looking for a mate.  Unfortunately, the lures have proven ineffective when dealing with small orchards or backyard fruit trees because mated females can come from nearby sources to lay fertile eggs on the apples.  Infested trees close to large apple orchards using lures for codling moth management increase the amount of spraying needed to keep the codling moth out of those orchards.

What about the insect traps advertised in garden catalogs?  Won=t they work in controlling the adult codling moth and cherry fruit flies?  The catalogs may be misleading you.  Codling moth traps are good tools to use to monitor the presence of these pests, but are not effective in eliminating damage because they attract only the male moths looking for a mate.  Again, fertile females can come in from nearby sources to lay eggs.. The yellow color and an ammonium carbonate bate on cherry fruit fly traps are what attract both male and female adult flies.  However, the traps are not considered adequate for good cherry fruit fly control.

Is diazinon still available to home gardeners to use on apples and cherries?  What pesticide can I use to control codling moth and cherry fruit fly?  There is still a number of home garden diazinon products commercially available that can be used on backyard cherry trees but only a few products are labeled for use on apples.  However, these products may not be readily available at your local garden store.   If you find a home garden product containing diazinon, be sure the label says it can be used on the type of fruit tree you have.  It is illegal to use the product on cherries or apples if they aren't listed on the label.

You may want to look for a home garden insecticide product containing a combination of malathion and methoxychlor for use on apples.  There are quite a few of these labeled as Afruit tree spray@ or Ahome orchard spray@ and most also contain a fungicide, captan, for disease control. 

Why shouldn’t I grow hawthorns and crab apple?  Their fruit also becomes infested with codling moth and can pose the same threat as infested apple trees do to commercial orchardists.  If you have a hawthorn or crab apple in your yard and it=s infested with codling moth, you must spray it regularly.  

How about ornamental flowering cherries?  Are they a problem for commercial growers?  Your ornamental Japanese flowering cherries don=t produce fruit and shouldn’t pose a threat to commercial cherry growers.  However, sometimes the rootstock from below the graft of a flowering cherry starts to grow.  It will usually be a cherry that produces fruit.  These shoots from the understock should be removed when they appear.  If the understock is the only part of the tree that=s still alive, then the entire tree should be replaced. 

Since apples and pears require so much spraying to keep them worm free, are there any other types of fruit trees I can grow without a lot of spraying?   There are no common wormy pests of apricots, peaches, nectarines, and plums that require regular spraying of the trees.  Your best bet is to grow plums, they don't require regular spraying and have a more reliable crop than peaches or apricots.

The Horsechestnut or Buckeye

The Horsechestnut or Buckeye
Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist
The common horsechestnut (Aesculus hippocastanum)is a big tree at maturity reaching 75 to 100 feet in height with a spread of 40 to 70 feet. You can see one of these big guys at the Benton County Courthouse in Prosser.  As you will note, this tree is best suited to parks, arboretums, and building with large expanses of lawn area.  It really isn’t one that most people should plant in their yards.
The nuts are produced in spiny capsules which are a nuisance with the large numbers produced by a mature tree. The nuts, with and without the spiny capsules around the outside, are popular ammunition for children.  While you can’t eat these nuts, they are fun to collect.  You can even start you own horsechestnut tree quite easily.  Just take some moist potting soil and place in a plastic container with a cover.  Bury several nuts in the potting soil.  Close the container and put it in the vegetable bin of your refrigerator for three months or more.  Late next winter or early in the spring take them out and plant them outside where the soil will be kept moist.  Treated this way, the nuts will germinate and grow.  If you give this a try, only use fresh nuts and “plant” them in your refrigerator soon after harvest.  If the nuts dry out, you’re out of luck.  This is an activity kids will love to help you with.  Just make sure you have room to grow this big tree.
Here’s a special note about chestnut “nuts.” Native Americans did use horsechestnuts as a food source, but only after they leached out their poisonous compounds in boiling water.  However, horsechestnuts should definitely be considered poisonous.   
The edible chestnut looks quite different from the inedible horsechestnut.  The edible chestnut has a dense, dangerously spiny capsule and the horsechestnut has a capsule with shorter, less dense spines.  The edible chestnut is somewhat rounded with a slightly pointed end.  The horsechestnut is smooth with no point and sometimes flattened a bit on one side.  Looking at the tree’s leaves also helps.  Horsechestnut leaves are compound and consist of five or more “fingers” or leaflets. Edible chestnut leaves are single, entire leaves.


Verticillium Wilt, A Disease That Attacks Trees From Inside Out

Verticillium Wilt, A Disease That Attacks Trees From Inside Out

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

It’s a disease that becoming more of a problem in our region.  Its name is verticillium wilt.  Verticillium wilt is a fungus disease that attacks over 300 woody and herbaceous host plants.  While it can be a problem in the vegetable and flower garden, its attack of woody plants is what creates the most havoc for home gardeners. 

Imagine a lovely, healthy maple tree in your front yard... growing well with the proper watering, fertilization, and good care that you’ve provided over the years.  One summer half the tree suddenly wilts and dies.  This scenario could happen if your tree is attacked by verticillium wilt.

There are lots of tree species it can attack, but there are some that it commonly attacks in our region.  These are maple, ash, catalpa, redbud, smoke tree, sumac, and Russian olive... with maple being the tree most often attacked.

Verticillium wilt fungus is a sneaky disease, entering a plant through the roots in the soil.  Infections are not obvious like some other diseases, such as powdery mildew or sycamore blight.  Symptoms can be acute... with leaf curling and drying, abnormal red and yellow coloring of the leaves, partial defoliation, wilting and dieback of branches.  This wilting and dieback will typically develop on one main branch, a sector of the crown, or an entire side of the tree.  Chronic symptoms are stunted growth, yellowish leaves, crispy brown edges on the leaves, slow and stunted growth, heavy seed crops, and branch dieback. 

Trees with verticillium wilt may limp along for years, exhibiting symptoms some years and other years not showing up at all.  However, the disease can suddenly attack a completely healthy tree causing it to wilt and die in a short period of time.

The first outward symptoms of verticillium wilt are leaf scorch, abnormal coloring, and dieback of branches.  However, there are many things that cause the same symptoms.  Girdling and encircling roots, root and crown rot, drought stress, compacted soil, trunk injury, and improper planting can all cause similar symptoms.

When verticillium wilt is suspected, a pocketknife should be used to make a slanted cut on an affected branch.  When verticillium wilt is present the cut may reveal streaking or discoloration of vascular tissue (transport) tissues in the wood.  In some species, like maple, this streaking is olive-green, but it varies from tan or brown to green or even black in some species. 

What causes this streaking?  The verticillium fungus once inside a tree, invades the xylem which is the water conducting tissue in roots, trunks, and branches.  The fungus produces toxins that can kill cells, even cells not close to the infected tissues.  The disease spreads in the plant by spores.  New fungal spores move upward with water in the vascular tissue.  The spores then lodge in healthy vascular tissue and new infections begin.  Dead and discolored tissues develop at the sites of these infections, first appearing slightly discolored and then developing the characteristic color for the species.  It’s this discoloration that causes the diagnostic streaking in vascular tissue.

The infected tree reacts to this fungal invasion by trying to block its spread.  It does this by producing gums and tyloses (chemical substances) in the vascular tissue to block fungal movement.  However, these gums and tyloses also impede the flow of water.  This results in the external symptoms of verticillium wilt that can be confused with other causes that also deter a tree’s uptake of water.

When looking for streaking in a recently wilted branch, the first place to look for streaking is directly under the bark.  If no streaking if found there, a deeper into the sapwood may reveal streaking.  However, streaking may not be evident even if the plant is infected with verticillium wilt.  It typically is not present in recently infected sapwood and is usually not found in twigs of one inch in diameter or smaller.  Streaking will most likely be found near the base of the tree, since the initial infection route is usually through the roots.  As you move up the tree, you’re less likely to find streaking.  To make diagnosis even more difficult, there is no detectable streaking of vascular tissues on certain species, like ash.

Before we talk about management of verticillium wilt, let’s talk a just a little more about it’s life cycle and how it enters a tree.  The wilt’s microsclerotia, which are tiny black resting structures, can be found in many soils.  They spread by wind or water.  They can also be introduced into “clean” soil from contaminated seed and plants or from contaminated soil on root balls, hand tools, or machinery.  They can exist in the soil for many years, up to 15 years, without contact with a host plant.  Lying in wait, the microsclerotia will germinate and infect a new plant when they come in contact with the roots of a susceptible host.  They invade the roots through a wound or by direct penetration.  Once inside the host, the fungus gets into the vascular tissue and spreads throughout the plant by spores. 

So how do we control the disease?  Plain and simply, you can’t control verticillium wilt once a tree is infected.  No fungicides have been found to be effective against the fungus in trees.  Injections of fungicides into a tree have been tried, but the results have been inconclusive.  You may not be able to control verticillium wilt, but you can try to manage it.  Just because a tree is infected, doesn’t mean it will die.  It may recover and be able to live with the disease... with careful management.

Trees should receive plenty of water to promote growth and avoid stress.  Infection is less severe when trees are not drought stressed.  A good deep soaking once a week during hot summer weather will help.  Fertilization with ammonium sulfate, when symptoms are first noticed, is recommended by many “verticillium wilt” experts.  Research in Michigan indicates that you should avoid applications of nitrate fertilizers because they ineffective in management of the disease.  While fertilization is part of the management program, you should avoid excessive fertilization, which apparently can increase problems with the disease.

You will want to promptly remove branches killed by the disease but you shouldn’t remove them until you give the water and fertilizer a chance revive recently wilted branches.  If they don’t come back in response to the extra care, remove the branches, cutting well below any of the streaking or discoloration and back to a main branch or limb.  Be sure to make proper pruning cuts and don’t leave stub cuts.  In between cuts, disinfect your pruning sheers with 70 per cent rubbing alcohol or a 10 per cent bleach solution.  Wood from infected branches should be removed and destroyed.  Chipping the wood and using it for mulch can spread the disease to other areas.

If a tree dies and needs to be replaced, keep in mind that the microsclerotia can remain in the soil for over 15 years.  When replanting, select a species of tree that is resistant to the disease.  Trees reported to be immune or resistant to verticillium wilt include beech, birch, ginkgo, honeylocust, sycamore, hophornbeam, sweetgum, pear, mulberry, apple, hawthorn, willow, white oak, bur oak, and sycamore.  Dogwood and linden appear to be susceptible to some strains of verticillium and resistant to others.  Fir, spruce, pine, juniper, and arborvitae are also resistant.

Sycamore Problems

Sycamore Problems

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent

Lace Bugs

Just this past week, several people have brought me samples of ailing sycamore trees.  On each of these samples there were two problems worth mentioning.  One problem was an insect, the sycamore lacebug.  It’s a tiny bug with lace-like wings.  It sucks sap from leaves creating a speckled appearance. The lace bugs can be found on the undersides of leaves along with small black specks of their excrement.   When feeding is severe, the leaves take on a brownish or dry look. 

The lace bug has not become a serious annual problem on sycamores, but it does show up from time to time.  The amount damage it causes is typically insignificant and tends to only become extensive in late summer or early fall.  With damage occurring so late in the season, control is not needed.

Herbicide Injury

The other problem evident on these samples was more noteworthy.  The leaves were somewhat malformed and cupped downward with an excess of the leaves’ natural hairy fuzz.  This is a sure sign of herbicide injury.  It was very likely caused by applications of “weed and feed” products to the lawn.  Dicamba or 2,4D, commonly found in “weed & feed” products, were probably the herbicides at fault.  Sycamores are particularly sensitive to damage from these two herbicides.

The downward cupping of the leaves is not critical. After all, the tree will soon be losing these leaves in preparation for winter.  The real damage from these lawn herbicides happens to the trunk of the tree.  Both herbicides can lead to damage of bark tissues and the emergence of bark eruptions on the main trunk, usually more extensively on the lower portions of the trunk.  The bark loses its beautiful mosaic pattern and smooth appearance.  It becomes rough and fissured.  Immediately beneath the eruptions, the bark tissue is pink and spongy.  Beneath the eruptions, the inner wood becomes dark brown.  This damage may later attract a borer, the American plum borer, which then causes even greater damage to the bark and trunk tissues.

Dicamba and 2,4 D can cause damage to sycamores even when applied at the correct rate, but greater damage occurs if they’re over-applied.  Over-application often occurs when home gardeners don’t calibrate their drop-spreader or sprayer before applying a “weed and feed”.  As a rule, 2,4 D and dicamba should not be applied in a general application to the lawn over the root zone of sycamores.  Spot treating weeds is safer for the sycamores and more economical.

Leaf Scorch

Yet another problem being noted by some sycamore owners is leaf scorch.  This shows up as bright yellow to brown leaves scattered throughout the crown and accompanied by substantial leaf loss.  The leaves most severely affected are the oldest... especially the inside leaves.  The most likely cause of this problem is heat and drought.  It’s been a hot summer.  Sycamores are big trees and if they don’t get enough water they let you know.  Lack of deep watering, girdling roots, and compacted soils can all be factors in a sycamore becoming drought stressed.

Trees to Consider

Trees to Consider

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

Smaller SpecimenTrees for the Home Landscape

AMUR MAPLE (Acer ginnala) 15-25'. A multi-stemmed tree. Excellent as a specimen tree with striking red fall color and clusters of small fragrant, yellow flowers in early spring. Winged fruits add interest. Tolerates wide range of soil conditions and heavy pruning.

HEDGE MAPLE (Acer campestre) 25-35'. A nice maple for use in the home lawn. Withstands severe pruning. Tolerant of alkaline soils. The very dense crown will need thinning to permit grass to grow below.

TATARIAN MAPLE (Acer tataricum) 15-20'. A small tree for planters or street locations. Tolerant of adverse conditions. Red to red brown fall color.

EUROPEAN HORNBEAM (Carpinus betulus) 40-50'. Durable small to medium tree. Also available in smaller columnar form.

RED BUD (Cercis canadensis) 20-30'. Heart shaped leaves, early purplish-pink flowers. Tolerant of alkaline soils.

PAGODA DOGWOOD (Cornus alternafolia) 25'. White flowers in May-June. Horizontal branching habit. Very hardy. Not very available.

FLOWERING DOGWOOD (Cornus florida) 20-40'. A favorite of many people but it is difficult to establish here. It needs pampering with protection, careful watering, acidifying fertilizers, and an organic mulch. It does better in partial shade!

KOUSA DOGWOOD (Cornus kousa) 20'. Early summer flowers and bright red fruit make this shrub-like tree an interesting specimen. Fruit can be a litter problem if near walks, patios or driveways. Rich red fall color!

CORNELIAN DOGWOOD CHERRY (Cornus mas) 20-25'. Small shrubby tree. Very early yellow flowers.

GOLDENRAIN TREE (Koelreutaria paniculata) 30-40'. Attractive yellow flowers, excellent as a small lawn tree, tolerates our climate and soil conditions well.

SAUCER MAGNOLIA (Magnolia soulangiana) 20-30'. Beautiful spring flowers. Prefers acid soils.

STAR MAGNOLIA (Magnolia stellata) 15-20'. Shrub-like tree with beautiful fragrant flowers. Prefers acid soils.

FLOWERING PLUM, CHERRIES, ETC. (Prunus sp.) Many different forms of different sizes, shapes, fruiting and flowering characteristics. Many are worthwhile. Consult: Manual of Woody Landscape Plants by Michael Dirr, Sunset Western Garden Book, and The World of Trees from Ortho.

CALLERY PEAR CULTIVARS (Pryus calleryana) Variable size, according to cultivar. Good flowering and fall color.

JAPANESE PAGODA TREE (Sophora japonica) 50-75'. Lovely flowers, difficult to establish, good tree for city lots.

JAPANESE STEWARDIA (Stewardia pseudocamellia) to 30'. White camellia-like flowers in June, rich red-maroon fall color, unusually mottled bark.

Large Shade Trees for the Home Landscape

RED HORSECHESTNUT (Aesculus x carnea) 30-40'. This tree is not for small yards. Its true beauty is its dark green foliage and deep red flowers. Very showy when in bloom.

RED MAPLE (Acer rubra) 50-70'. Rounded tree with good red fall color. Good for poorly drained sites.

SUGAR MAPLE (Acer saccharum) 60-120'. This is an excellent shade tree but it needs plenty of room. Orange to yellow fall color. Has some disease problems.

RIVER BIRCH (Betula nigra) 40-70'. This birch does best in moist soils and prefers an acid soil, but can be grown here if acidifying fertilizer is used. One of the most trouble-free birches and is resistant to bronze birch borer. It has an apricot colored peeling bark that is an attractive feature. ‘Heritage’ is a considered a superior selection that has good vigor and grows relatively fast.

WHITESPIRE WHITE BIRCH (Betula platyphylla japonica 'Whitespire Senior'). The only white barked birch which is bronze birch borer resistant. You must have 'Whitespire Senior' for resistance to borer.

GREEN ASH (Fraxinus pennysylvanica) 50-60'. A popular shade tree with two bad points. It has a big problem with aphids and other insects and the seeds and seedling create a nuisance. Look for 'Marshall's Seedless' cultivar for a seedless vigorous tree. Ash borers are beginning to devastate this tree and you may want to reconsider planting it.

THORNLESS COMMON HONEYLOCUST (Gleditsia triacanthos var. inermis) 30-70'. A "perfect" tree for filtered shade. A relatively new insect problem (honey locust pod gall midge) had made the tree less than "perfect." Avoid the 'Sunburst' cultivar because of this insect pest.

KENTUCKY COFFEE TREE (Gymnocladus dioicus) 60-75'. This large tree is adaptable to our harsh growing conditions. Its bark has an interesting pattern. One problem with this tough tree is the litter it creates with its seed pods and leaves. Use only in large areas.

AMERICAN SWEETGUM (Liquidambar styracifula) 60-75'. Needs room to develop roots but it is a nice tree with excellent fall color and corky bark. Prefers an acid soil and should be fertilized with an acidifying fertilizer. Few insect problems in our area. 'Moraini' is an excellent cultivar with a faster rate of growth.

AMERICAN HOP HORN BEAM (Ostrya virginiana) 25-40'. A nice, medium sized tree with many horizontal and drooping branches. Tolerates partial shade. Slow to establish.

PERSIAN PERROTIA (Parrotia persica) 20-40'. Here’s a tree with few pest problems and it has very nice shiny leaves and exfoliating bark. It’s yellow-orange-scarlet fall color is unsurpassed by any other tree. This is the perfect landscape tree. If you can find it, plant it.

LONDON PLANE TREE (Plantanus x acerifolia) 70-100'. Warning: this is a sycamore and it's a BIG tree! Select only anthracnose and powdery mildew resistant cultivars. One cultivar, `Yarwood’ is very resistant to powdery mildew and fairly resistant to anthracnose. ‘Bloodgood’ is very resistant to anthracanose. `Liberty’ and `Columbia’ are two other cultivars that have been touted as being anthracnose resistant, but they’re apparently only resistant to eastern strains of the disease and not western strains of the disease.

RED OAK (Quercus rubra) 60-75'. An oak with relatively fast growth. Red fall color. Relatively few insect and disease problems. Interesting furrowed bark. This tree needs room, give it plenty of space to grow into.

ENGLISH OAK (Quercus robur) 40-60'. Tolerant to eastern Washington conditions. Also a narrow columnar form is available.

LITTLELEAF LINDEN (Tilia cordata) 60-70'. An excellent shade tree. Aphids may be a problem. Can be pruned into a hedge form.

SILVER LINDEN (Tilia tomentosa) 50-70'. A very nice shade tree with attractive foliage. Top of leaves are green, bottom sides are silver. Fragrant flowers in July. Tolerates heat and drought fairly well. Nice smooth gray bark. Aphids may be a problem.

CHINESE ELM (Ulmus parvifolia) to 50'. Small to medium sized tree. Relatively problem free. Interesting mottled bark. Quite drought and alkaline soil tolerant. Not to be confused with the Siberian Elm (Ulmus pumila).

JAPANESE ZELKOVA (Zelkova serrata) 50-80'. A handsome tree with an interesting growth habit. Somewhat difficult to establish. Look for the cultivars 'Village Green' and 'Halka'.




Mulching Trees is Good and Bad

Mulching Trees is Good and Bad

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

It seems to be human nature... if something is good, a lot is even better.   Unfortunately, that’s not always the case.  For example, one of the best things you can do for the trees in your yard is to mulch them with an organic mulch.  Excessive amounts of mulch applied improperly by enthusiastic gardeners can cause more harm than good.  I want to talk about the problems caused by excessive and improperly applied mulch.... but first let’s review the benefits of mulching along with the proper way to apply mulch.

Benefits of Mulching

Competition with Turf  —  Trees and turf are competitors that don’t get along particularly well.  They compete for the same water and nutrients that are available in the top foot of soil. Because grass roots colonize faster and take up more of the soil space, they often “win” the fight for nitrogen in the soil.  Both struggle against each other for the available water. They also compete for light, with trees having the uncontested advantage because of their height.  As they get taller and wider, trees intercept so much light that the grass growing in the tree’s shade can’t get enough light.  As a result the grass thins out.

Grass has a secret weapon in its fight against trees. Grasses apparently release antagonistic chemicals into the soil that slow the growth of tree roots. This phenomenon is referred to as allelopathy. Researchers have found that tree growth is reduced when trees are grown in turfed areas compared to trees with mulched root systems. They attribute the improved growth of mulched trees to the absence of these antagonistic chemicals along with the other benefits provided by mulches.

A layer of mulch over the entire root zone of trees reduces the contentious competition between trees and turf... allowing both to grow better in peace.

Conserving Moisture  —  Mulching conserves moisture by reducing the amount of water that’s lost through evaporation from the soil surface.  A layer of mulch reduces the amount of water that must be applied by irrigation.

Adds Organic Matter to Soil  —  As organic mulches decompose they improve soil fertility and structure.  Decomposing organic mulches also provide food and a favorable environment to beneficial soil organisms, such as earthworms and “good” fungi.

Provided Insulation  —  A layer of mulch acts as insulation for tree roots, protecting them from extreme summer and winter temperatures.

Discourages Weeds  —  Mulches discourage weeds, which also compete with trees for water and moisture.

Reduces Soil Erosion  —  Mulches reduce soil erosion and soil compaction, as well as improving water entry into the soil.

Protects Trunk  —  A circle of mulch around a tree decreases the chances of damage to the tree trunk from string weed trimmers or mowers.

Looks Nice  —  An attractive layer of mulch around trees and shrubs provides a more uniform look to a landscape.

The Proper Way to Mulch

So just what is the “proper” way to mulch trees?  Proper mulching involves applying a two to four inch layer over the area around the trunk, extending out to the dripline or beyond.  The larger the area, the more beneficial to the tree. The ideal way of mulching is to apply mulch over the entire root system... which can be an area as much as two to three times the spread of the branches and extending well beyond the dripline.  The practical way of mulching is to apply mulch to an area at least four to five feet in diameter around the trunk.  However, it’s very important to keep the mulch six inches away from the trunks of young trees and one foot away from the trunks of older, mature trees.

A well-aerated, composted organic mulching material is best for properly mulching a tree.  Some of the preferred materials for mulching trees include bark, grass clippings, shredded leaves, and pine needles. If grass clippings are used they should be mixed with some coarser materials to discourage matting.  Wood chips make especially good mulch if they’re composted first and then mixed with leaves and bark.  Fresh wood chips and sawdust should never be used because their decomposition ties up available nitrogen in the soil, depriving the growing tree of nitrogen needed for growth.

Improper Mulching Can Kill Trees

Improper mulching or mulching mistakes are easy to make. One of the most common mulching mistakes is over-mulching.  Too much of a good thing isn’t better... in this case it can kill trees by suffocation.  When too much mulch is applied, it limits the amount of oxygen that’s getting to the roots of the tree. The excessive mulch also slows evaporation of soil moisture and the soil stays wet for long periods.... exacerbating the lack of oxygen in the soil.

Another common mulching mistake is placing the mulch against the trunk of the tree.  The base of the tree where the trunk flares out must be able to “breathe” .  It’s not root tissue and can’t tolerate a continually moist environment or a lack of oxygen.  Frequent irrigation that keeps a tree trunk saturated, a change of grade that buryies the flare, or mulch applied directly to the base of a tree can cause the death of the inner bark.  When the inner bark dies, the tree is no longer able to send food to its roots and the roots eventually starve.  Without roots that can take up water and nutrients, the tree dies. Excess moisture at the base of the tree can also favor bacterial and fungal diseases that attack and kill inner bark tissues. 

A very thick a layer of materials that are not fully composted, such as a thick layer of green grass clippings, can also lead to trouble.  This thick layer may actually heat up and go through the composting process, much like a compost pile.  The heat of early decomposition may lead to temperatures as high as 120 to 140 degrees in the mulch layer.  If this “composting” mulch is directly in contact with roots or trunk tissues, these temperatures can kill them.

Excessive insulation from a very thick layer of mulch can delay the hardening process in the fall, making a tree more susceptible to winter injury from cold temperatures, especially those occurring early in the winter.

When mulching was first advocated, some enthusiastic gardeners applied thick layers of mulch to their trees.  They later found that as a result of this thick layer the tree roots grew close to the soil surface... probably because they needed air.  These shallow roots didn’t have problems until severely cold temperatures arrived, killing them... and the trees.

Finally, a more recent and interesting way to improperly mulch trees are with mulching “volcanoes.” Mulching volcanoes occur when gardeners apply a tall pile or mountain of mulch (or sometimes soil) around the base of the tree.  These do nothing to help a tree... and are an easy way to kill it through suffocation and collar rot. 

So remember... mulch is very good for trees, but a lot of much mulch or mulch that’s applied improperly is bad for



Windbreak Trees

Windbreak Trees

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

It's been said that the Tri-Cities is a windy area. You betcha! You’ll get no argument from most area residents.  Wind erodes our soil and leads to nasty dust storms. Winter winds can increase a home's heating costs by 10 to 40 per cent.  Wind can also be just plain annoying.  You can't stop the wind, but you certainly can slow it down with strategically placed trees and shrubs ... windbreaks.

"A windbreak is a planting usually of both trees and shrubs that is designed and established to reduce the undesirable effects of strong winds," says Don Hanley, WSU Extension Forester.  Early settlers in the treeless areas of Washington and the rest of the Northwest needed trees to provide much needed shade and protection from the wind. Farmers planted fast-growing species of trees in a simple one to six row design. Single species of trees, such as eastern cottonwood, black locust, and Lombardy poplar, were planted fairly close together.  Not all these windbreaks were successful ... improper placement or poor selection of the tree species meant a failure to obtain the goal of diminishing the wind.

Things haven't changed much since the days of those early pioneers.  Farmers and homeowners are still planting windbreaks and still having limited success.  The main reason for the failure of windbreak plantings is that many are not given adequate care to get them off to a good start.  Plantings often succumb to a lack of water, competition from weeds, damage by livestock, mechanical injury from mowers and other equipment, and careless use of weed control chemicals. Windbreak plantings are just like any other landscape planting, the trees need care and attention to be able to live and grow.

While the pioneers had to guess what trees to use and where to plant them, scientific research has revealed the proper design, location, and types of trees that will provide the most effective windbreaks.


These are the things you should consider when planning your windbreak:

  • The location that the windbreak will be most effective.
  • Do you have enough space for a windbreak?  How many rows will you plant?  The most effective windbreak has five rows of deciduous and evergreen trees and shrubs.
  • What species are best adapted to the area and your situation?
  • Is there irrigation available to provide them with the needed water for establishing and maintaining them?
  • Will the trees create a problem when they reach their mature size?


Our local prevailing winds tend to come from the west, but this may vary slightly depending on your situation and topography. A windbreak should be located so that it’s at a right angle to the prevailing winds, or as nearly as possible to a right angle. The closer it is to the right angle, the more effective it will be.

To be effective, the windbreak should be no more than 100 feet from the house.  At this distance, trees 35 or more feet tall break and lift the wind currents over the top of the home,  You can place the windbreak closer but make sure the trees don’t shade the house. 

The windbreak should also extend fifty feet beyond the length of the house and the area you want protected.  If you must have gaps in your windbreak rows to accommodate irrigation ditches, paths, driveways, etc., try to make the crossings at oblique angles so you don’t create your own sort of “wind tunnel.” 

Number of Rows

Many people usually plant only one-row windbreaks. However, the more rows you plant, the more effective the windbreak.  If there is not enough room available for a full five rows, consider four or less rows. Be sure not to crowd the rows though.  Crowding slows growth and weakens the plants. Lower limbs of crowded trees tend to die out due to heavy shade.  Trees should be staggered between rows.

If there is only room for four rows, the best protection is achieved with a row of dense shrubs, a row of medium evergreens, a row of tall evergreens, and a row of medium evergreens.  With three rows you’ll get the maximum protection with single rows of a dense shrub, a tall evergreen, and a medium evergreen.  With two rows, you’ll want to use a medium evergreen and a tall evergreen. If you only have room for one row ... use a tall evergreen, such as arborvitae.


The spacing between rows should be sixteen feet.  The spacing between plants in the rows should be:

Tree/Shrub Type

Multiple-row Windbreaks

Single-row Windbreaks

Dense Shrubs



Medium Deciduous Trees



Tall Deciduous Trees



Medium Evergreen Trees



Tall Evergreen Trees



These spacings give the trees and shrubs room to develop full dense crowns before they start growing together.

Another option for design is a twin-row, high density windbreak which can be used when space between the home and planting is limited.  With this high density design, the two rows of trees are planted six feet apart and the trees are planted five to eight feet apart within the rows.  The same species may be used in the twin row.  Additional twin-rows can be placed 25 to 50 feet away, allowing for the planting of gardens between two twin rows.  The distance of 100 feet between the house and the windbreak can be reduced. The spacing of the trees facilitates watering by drip irrigation. 


No windbreak will succeed if the plants aren’t planted right.  As with any landscape planting, you should prepare the soil first.  You may find it easiest to till the soil along the row.  Till the soil to a depth of 18 inches, or more if possible.  Then dig a trench deep enough to accommodate the roots of the trees. The top of the root ball should be at soil level or just a little above to allow for the soil settling.

Place the trees in the center of the trench or hole so that all the tree roots are in a downward position. Hold the tree while filling the soil back in around the roots.  This is probably easiest when done by a team of two people or more.  Gently firm the soil around the roots and then water the trees in with a thorough application of water.

Apply a slow release fertilizer at the rate recommended on the label. Don't over-fertilize because the fertilizer salts can damage the young roots of the plants. 

You can encourage growth of the trees and shrubs by topdressing with an application of fertilizer each spring just as new growth starts to unfold. Look for an acidifying fertilizer to help lower the pH or alkalinity of the soil. This is most important with evergreens because they generally prefer slightly acid soils.  Many local soils are quite alkaline, unless they have been under irrigation for years.

 Weeds and grass growing around the trees can impede growth by robbing them of needed nutrients and moisture.  A three to four inch thick layer of wood chip or bark mulch will be beneficial in keeping down weed growth and maintaining soil moisture.  Mulch the entire root zone if possible, but keep the mulch several inches away from the tree trunk.

The most successful windbreaks are those with live and growing trees.  Provide the needed water and care to help the trees establish and thrive.  Be sure to provide protection from animal and equipment damage. 

Time To Grow

If planned and planted properly, it will only take about three to four years before you start noticing the protection that your windbreak is providing.  Within seven years the windbreak should be providing effective protection to you and your home.

For more detailed information contact your local WSU Cooperative Extension office for the bulletin "Trees Against the Wind."

What Types of Plants Do Best In Windbreaks

Early pioneers planted a variety of fast-growing, soft-wooded, short-live tree species, such as Lombardy poplar, willow and cottonwood, for their windbreaks. Many of these fast-growing trees are still recommended and used for modern farm windbreak use.  However, homeowners should be aware that most of these are very invasive and have extensive root systems that can be a problem with septic systems, driveways, swimming pools and elsewhere.  These species also tend to be short-lived, such as with poplars which start to decline after about fifteen years.  The only advantages to using them are that they are inexpensive and they grow quickly. There are better plants that will provide more effective, long-term windbreaks.  Here are some:

Deciduous Shrubs

Mature Height (feet)

Crown Height (feet)

Common lilac



Tartarian honeysuckle



Common privet



Nanking cherry



Tall Evergreen Trees




Evergreen Shrubs

Mature Height (feet)

Crown Height (feet)

Mugho pine




Deciduous Trees

Mature Height (feet)

Crown Height (feet)

Fastigiate European hornbeam



Fastigiate English Oak



Littleleaf Linden



Hedge maple



Evergreen Trees

Mature Height (feet)

Crown Height (feet)

Arborvitae(Northern White Cedar)



Scotch pine



Austrian pine



Blue spruce



White fir



Nordman fir



Douglas fir



Rocky mountain juniper



Eastern juniper




Franklinia and Chitalpa Trees

Franklinia and Chitalpa Trees

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

You’ve probably never heard of the Franklinia tree or the chitalpa tree.  They’re both uncommon trees that you’re not likely to find growing in this region. However, I think it would be interesting to try them and see how they well they would grow here. Don’t run to your local nursery and ask for these trees.  They’re not readily available and will probably only be something you can find in a specialty nursery catalog.

Let’s talk about the Franklinia tree.  It has a fascinating history.  It was first discovered in 1765 in Georgia by John Bartram of Philadelphia.  While Bartram’s occupation was that of gentleman farmer, he also studied philosophy, religion, medicine, and science.  It was his interest in plants and botany that gained him a place in history.  He made many botanical expeditions throughout the “New World” and earned himself the title of King’s Royal Botanist for North America from King George III of England.  

It was on one of his expeditions to Florida that John and his son William came across a beautiful blooming tree or shrub along Alatamaha River in Georgia.  Because they were anxious to reach their destination, they didn’t stop to collect samples. Ten years later William headed back to Georgia in hopes of finding and collecting specimens of this special plant.  He found the plant, retrieved specimens, and took them home to propagate them. William named the plant, Franklinia alatamaha, after his father's good friend Ben Franklin.

What makes the story interesting and the plant so rare, is that when a visit was made to the same location in 1803 the plant had disappeared.  No other native stands of this particular plant were ever found again.  It’s believed that all the specimens of the Franklinia tree in the United States and around the world come from those collected and propagated by William Bartram.

Apparently the Bartrams saved the Franklinia tree from virtual extinction.  This makes the tree very fascinating, but it’s the tree’s characteristics that make it truly special.  It’s a cousin to the camelia.   Large white flowers emerge from marble-size buds in late summer and continue coming along well into fall.  The flowers are three inches in diameter with an orange center and a delicate fragrance.  These remarkable flowers are sometimes still present when the tree starts to turn orange to red in the fall.

The Franklinia tree is a small deciduous tree or large shrub with an upright spreading form and an open base.  It usually only grows to about twelve feet in height, but there have been reports of taller trees. The tree is slow growing and difficult to transplant.  It requires a moist, acid, well-drained soil that high in organic matter.  While the Franklinia tree is winter hardy for our area (USDA Zone 5), it may not do well here because of our intense summer sun.  If tried in our region, it should be planted where it will be shaded from the sun during the heat of the day.  It would also be best to prepare a landscape bed for this special tree by adding compost or peat moss to the soil, along with mulching the tree with bark or compost and keeping the soil evenly moist. 

If you know of one growing in this region, let me know.  Last year to commemorate the 300th anniversary of John Bartram's birth, Martha Leigh Wolf of the historic Bartram's Garden in Philadelphia started a census of Franklinia owners wanted to “find out how far north and west the fabled plants grew, under what conditions they thrived, how long they could live, and how big they could get.”  They surveyed members of the American Association of Botanical Gardens & Arboreta and the Garden Writers Association of America. What they thought would be simple survey turned out to be much bigger with replies far beyond their expectations.  The little survey evoked hundreds of responses from all over the United States and as far away as New Zealand and Germany.  One gentleman even sent a picture of a Franklinia that he had taken in Korea in 1950.  Apparently, the Franklinia tree is beloved by its owners who know they are growing a very special and rare tree.

The chitalpa ( x Chitalpa tashkentensis) doesn’t have a similar rich history, but it is an interesting tree.  It’s not a native tree but a hybrid created in Uzbekistan by Nikolai Rusanov in 1964. It’s what is called a bi-generic cross... a cross between two genera of plants, the desert willow (Chilopsis linearis) and catalpa (Catalpa bignoides).   The chitalpa was first introduced into the United States by Robert Heff of the New York Botanic Gardens in 1977. 

The chitalpa is a fast growing deciduous tree or shrub with spreading‑arching limbs that form a dense broad-oval crown. The mature size is believed to be around 20 to 25 feet tall, but it hasn’t been around long enough to know for sure. This vigorous tree is drought resistant and able to withstand strong winds without breakage. 

The chitalpa’s parents are “messy” trees because of the litter they create with dropped flowers and many long seed pods.  However, the chitalpa is much better behaved. That’s because it’s sterile... not producing seed pods.  The sterile flowers also dry on the tree rather than dropping to the ground right after bloom. 

Perhaps the main drawback to growing the chitalpa in this region is that it may not be totally winter hardy.  It has withstood temperatures as low as nine degrees Fahrenheit, but it’s likely to die back to the ground after severely cold winters in our region. Its other characteristics that may be troublesome are is its tendency to sucker near the base and its susceptibility to mildew in cool weather. 

One of the best things about the chitalpa is its flowers.  The cultivar 'Pink Dawn’ produces numerous clusters of showy pale pink flowers in the summer.  Each cluster contains 15 to 40 one-inch long flowers with ruffled petals and lavender throats. The leaves are narrow and glossy.  Another cultivar ‘White Cloud’ is a bit less showy with white flowers.

It’s not easy to find sources of these two trees.  You can get both ‘Pink Dawn’ chitalpa from Forest Farm in Williams, Oregon at (541) 846-7269.

When Snow or Ice Bows and Breaks Tree

When Snow or Ice Bows and Breaks Tree

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

Heavy wet snow, freezing rain and ice can mean bowed and broken tree limbs and trunks.  What causes limb and branch breakage?  Certain types of trees, especially fast growing species, have "brittle" wood that is prone to breakage.  This includes Chinese elm, silver maple, boxelder, and poplar.  Some tree species have narrow branch angles, making them structurally weaker in situations like these.  The `Bradford' cultivar of callery pear is a good example of a tree with a weak structure due to narrow branch angles.

Another reason for structural weakness in a tree is past pruning practices.  Improper pruning practices, such as topping or stub cutting, leads to the development of poorly attached branches.  There is a great tendency for these branches to break off the tree as they grow larger and heavier, especially when stressed by strong winds or a load of snow and ice.

Trees also become structurally weaker when wood rot develops in the trunk and main branches.  Wood rot is the result of fungi, which invade the tree after physical damage occurs... through wounding, bad pruning cuts, and severe temperature damage.  Severe wood rot can develop through repeated wounding and large branches that have been topped.

Some trees broke under the recent heavy snow-loads but some only bent... bending or bowing was common on young deciduous trees, as well as on certain types of evergreens trees and shrubs.  The wood in these plants is more elastic, with wood bending instead of breaking.  In these cases, it was merely a factor of the snow and ice and the branches yielding to the weight.

Now what can be done about the injured trees and shrubs?  Let's deal with the "bent-out-of-shape" plants first.  According to Dr. Ray Maleike, Washington State University Extension Horticulturist Emeritus, "When snow or ice bend branches and entire trees out of shape, the offending snow or ice should be removed immediately and an attempt made to straighten the bent branch or trunk.  If the plant part isn't straightened very soon after the snow has stopped, the plant may remain bent over... permanently."  Collected snow can be removed with a broom.  Sweep upward to lift the snow off.  However, don't disturb the branches if they're heavily weighted and brittle with ice or you have a concern about the structural integrity of your tree.

Maleike suggests trying to physically straighten the plant or branch once you remove the snow.  He notes, "This doesn't always work, but it does occasionally.  If the young tree or shrub has been squashed down to where it extends into traffic areas, it may have to be pruned."

Around our area there a number branches on multi-stemmed, columnar-needled evergreens, like arborvitae, that have been bent out away from the plant.  Maleike indicates that these may be tied back to the main plant with a soft, non-chafing material like cotton clothesline or nylon pantyhose.  The tying materials may have to be left on for 6 months or more.  He notes, "Tying the plants together before the winter starts is a good preventative for this problem."

What can be done for small trees which have bowed over but have not broken or cracked?  These trees can be staked until they can stand on their own again.  Maleike recommends this procedure, "Drive two stakes, about six to eight inches away from the trunk, into firm ground. (Be careful not to severe major roots.)  Then tie the trunk to the stake at the lowest height, which stabilizes the tree in an acceptable upright position.  A nonchafing tying material must be used."

The stakes should not be left on indefinitely.  They should be removed as soon as the tree can stand by itself again.  This should be within the first growing season after the "bowing" occurred.

Trees with broken branches don't need immediate attention.  However, it's advisable to prune off broken branches as soon as the weather and circumstances allow.  Prune damaged branches back to another branch or the main trunk if necessary... don't make flush cuts and don't leave branch stubs.  On large branches this cut should be made to just outside the branch collar.  Be sure to follow recommended tree pruning practices.  When power lines, large limbs, or main branches complicate the matter, contact a trained and certified arborist.

With the breakage of limbs, sometimes bark is torn on the larger limbs or the main trunk.  To help the tree, the torn bark should be carefully trimmed with a sharp knife to make a smooth, rounded edge to the wound.  Cut only the bark and not into the wood.  No wound dressing materials are recommended for bark wounds or pruning wounds.

Ginkgo Trees — A Link to the Past and Good Trees for the Present

Ginkgo Trees — A Link to the Past and Good Trees for the Present

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

There’s a lovely row of old ginkgo trees in the parking lot at the WSU Research and Extension Center in Prosser,WA.  They were planted there many years ago and have grown into very nice specimens.   However, it wasn’t long ago that some employees wanted to have the trees cut down.  The problem was that several of these ginkgo trees have turned out to be female fruit producing trees.  The awful smell of the over-ripe fruit is what caused some to want the trees’ removed.  This is truly a nose-pinching smell akin to dog manure or worse. Pee-yuu! 

Although the smelly fruit do present a distinctly unpleasant problem, those at the center who wanted to keep these old ginkgo trees prevailed... and the trees have remained unscathed.  I’m glad.  Ginkgos are a living link to the prehistoric past... having originated over two hundred million years ago.  Once common in North America and Europe, the ginkgos were wiped out during the ice age and disappeared from North America seven million years ago and from Europe three million years ago.  Ginkgos were thought to be extinct until 1691 when a German physician and botanist, Engelbert Kaempfer, found ginkgos growing in Japan.

Kaempfer may have found the “lost” tree, but it was Buddhist monks who most likely saved this living fossil from extinction.  From about 1100 AD, Buddhist monks in the mountains of south-east China cultivated ginkgo trees in the courtyards of their monasteries.  The ginkgo trees were valued for their medicinal uses, edible seeds, and perhaps their beauty.  In about 800 AD, the monks brought the ginkgo with them to Japan where many years later Kaempfer found it.

Kaempfer was in Japan for two years (1690-1692) on a mission for the East‑India Company. When he wrote about his discovery in 1712 he called ginkgo trees "Amoenitatum exoticarum". At some point he brought ginkgo seeds to Holland.  It’s believed that one of the first ginkgos to be “replanted” in Europe was at the Botanical Garden in Utrecht ... where it’s still growing today.  In 1754, a ginkgo was planted at Gordon, the English botanical school, and in1762 at Kew Botanical Gardens.

From England, Holland, and Japan the ginkgo was gradually reintroduced to Europe and North America.  In 1784 a ginkgo was planted in William Hamilton’s garden in Philadelphia.  It then took about a hundred years for the ginkgo to become a popular street tree in east coast cities.  It was made more popular when famous architect Frank Lloyd Wright picked it as his favorite tree.  It’s now found in landscapes and cities across our country.

Not only is the tree’s “lost and found” history quite interesting, it’s an extraordinary tree in other ways too.  Botanists relish the ginkgo.  What particularly excites botanists is that the ginkgo has sperm that have flagellae, making them mobile.  Among living seed plants the trait of flagellate sperm is only shared with cycads.  These swimming sperm are found inside the ginkgo pollen grains. 

Ginkgo trees are dioecious with separate male and female trees.  The pollen is moved from male to female trees by the wind.  The female tree is pollinated in the spring when a pollen grain lands on one of its ovules.  However, actual fertilization of the ovule by the sperm doesn’t happen until the fruit matures, drops from the tree, and the stinky, fleshy seed coat rots away. 

Ginkgo bilobas are the only living members of the Ginkgo family which once consisted of at least 18 members.  All these other family members were lost millions of years ago. Ginkgoes are felt to be the link between ferns and flowering seed bearing plants.  

Unlike many other plants that have evolved in nature, the ginkgo has remained basically unchanged, probably thanks to the long cultivation by Buddhist monks.  Fossilized leaf material from270 million years ago is very much like the Ginkgo biloba of today.  That’s why Darwin called it a “living fossil”.  Botanists consider it a living wonder because it could be the oldest living seed plant in the world.

Ginkgoes are favored as a landscape and urban tree.  It’s a tough and durable tree with few insect pest or disease problems.  It’s also very resistant to pollution. It’s a hardy tree that does best in climates with wet winter weather and hot summers.  It does quite well in our region. The trees in Prosser are an example of their suitability for this area.

The tree itself is not especially pretty when young, but it does have an interesting growth pattern. As a young tree, it’s pyramidal in shape with a strong central leader.  Branches along this main trunk are regular, ascending, and asymmetrical.  The interesting growth of the ginkgo is due to its branching pattern.  The tree develops a combination of long and short branches that grow at right angles to the trunk and larger branches.  Its irregular growth pattern is attributed to the tips of larger branches sometimes becoming slower growing, shorter type of branches and the shorter side shoots changing to the faster growing, larger branches. 

The ginkgo’s unique bright-green leaves are produced alternately along longer branches and clustered at the tips of shorter side shoots. They’re two-lobed (“biloba”), fan-shaped, leathery, and smooth.  The veins fan out from the base of the leaf and aren’t cross-connected by smaller veins.  In the fall, the leaves turn a bright golden yellow and all drop off almost overnight with the first sign of cold weather.                          

The tree eventually grows to a height of 50 to 90 feet tall and 30 to 40 feet wide with a thick trunk, 13 to 30 feet in diameter.  Male trees generally have more of a columnar form, where females will have a somewhat wider crown.  As the trees age, they develop a wonderful grey bark with deep furrows.

Ginkgoes are a very durable tree.  Proof of that durability was found in Japan in 1945 after the atomic bomb was dropped on Hiroshima.  Human life was lost, buildings were obliterated, and plants were scorched and killed... except some ginkgoes survived.  Several ginkgo trees around the epicenter of the blast on a temple-site survived and resprouted without any visible genetic deformation.  Amazingly, two of these surviving trees still grow in Hiroshima today and are considered “bearers of hope”.

Remember that stinky fruit I mentioned earlier?  They look like yellow cherries and drop from the trees just prior to leaf fall.  It’s the fleshy outer covering that smells.  Inside a woody nut can be found. These nuts are a special food delicacy in China and Japan.

Today’s use of ginkgo leaf extract in a variety of natural medicines stems from its use in traditional ancient Chinese medicine.   The Chinese have used it to help with a variety of ailments.

It’s believed that ginkgo trees can live up to 3,000 years or more!  Ginkgo trees are honored trees in Asia where they have been seen as symbols of changelessness, unity, love, and hope and even possessing special miracle powers

Garden Note: If you want to plant a ginkgo tree, you may want to get a male tree.  They don’t produce stinky fruit, just the female trees do. However, female trees won’t usually flower or fruit until they’re about 20 years old!


New Ways to Control Worm Pests in Fruit Trees

New Ways to Control Worm Pests in Fruit Trees

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

If you own an apple, crabapple, pear or fruiting cherry tree, you may be wondering what to do about controlling worms in the fruit.  With apple, pear, and crabapple, regular sprays are needed to prevent the codling moth larvae from boring into and destroying the fruit.  These sprays start not long after full bloom and continue until close to harvest.  With cherries, regular sprays are needed to control the cherry fruit fly to prevent the cherry fruit fly from laying its eggs under the skin of developing cherries.  The eggs develop into those nasty Aworms@ or maggots found inside a cherry, destroying its palatability and storage life. The sprays for control usually start in mid-May and continue until close to harvest.

Because residents of Benton and Franklin counties live in a region with an important commercial tree fruit industry, they=re required by county law to control these wormy pests in any fruiting apple, crabapple, pear, or cherry trees on their property.   Infested backyard trees are a source of contamination for any nearby commercial orchard.  This can lead to commercial orchardists having all their fruit rejected by a packing house and the need to apply pesticides more frequently to keep their fruit worm free. 

Limited Pesticides Available to Prevent Wormy Fruit

Even responsible home gardeners are having an increasingly hard time controlling these wormy fruit pests.  The reason is that there aren’t many effective chemicals still available to home gardeners for use on fruit trees to control these pests.  In past years, weekly sprays of diazinon would control them, but diazinon will not be available after this year.  The limited diazinon products still available have very restrictive labels, limiting the number of times they can be applied to fruit trees during the growing season.

There are only two home garden products labeled for use in Washington containing combinations methoxychlor and malathion, two insecticides that can be used on apples and cherries for effective control of codling moth and cherry fruit fly. They are Ortho=s Home Orchard spray and True Value=s Greenthumb Liquid Fruit Tree Spray.  These may be difficult to find, but are available.  Methoxychlor-malathion mixes will provide adequate control when applied every 7 to 10 days.  There are also several products that contain malathion without methoxychlor and should also provide adequate control.

Clay Deters Codling Moth

One non-chemical material that can be used by home gardeners is a product called Surround.  Surround consists of highly refined kaolin clay.  Mixed with water, it=s sprayed onto trees.  The white clay particles coat the leaves and the fruit.  Researchers have found that rather than killing pests, this material acts as a repellent or deterrent to insects.  Insects do not like the coated surfaces and fail to deposit many, if any, eggs on the treated surfaces.  With some insects, the kaolin coating may simply hide the host plant from an insect=s chemical receptors, preventing the pest from finding the plant.

Unfortunately, while Surround has been extremely effective in repelling some pests, it=s not completely effective against codling moth, only reducing codling moth damage between 30 and 90 per cent from untreated controls.  Even if it was completely effective, home gardeners might not find treated trees aesthetically acceptable since the treated trees are coated with a chalky white coating, giving them a ghostly appearance.  In addition, the harvested fruit requires thorough washing to remove the kaolin coating.

One Product Not Available to Home Gardeners

University researchers and chemical companies are searching hard for effective materials to help control pests with less chemicals and less impact on the environment and beneficial insects.  One new product that has been developed is ALast Call@.  This is a paste that=s applied from a custom dispenser as droplets about the size of a small pea onto the trunks and main branches of each apple tree in an orchard.

ALast Call@ contains permethrin (an insecticide), a UV protectant to keep the material from breaking down too quickly, and an insect pheromone (sex attractant). The material is designed to attract the male moths to the droplet and then kill them.  After contacting the droplet and finding out it=s not a sought-after female moth, a male moth becomes paralyzed and quickly dies. ALast Call@ must be applied before the male moths have a chance to mate with the females.  That=s because the females aren’t attracted to the pheromone droplets.  Once they=re fertilized by the male moth, they start laying eggs... leading to fruit damage. Once the females are laying fertile eggs, it doesn=t matter if the males are dead or alive.

While ALast Call@ has provided positive results in commercial orchards, in a Utah State University research study it proved ineffective in controlling codling moth in home orchard sites.  The reason for this failure was probably due to fertilized females from outside sources (such as nearby unsprayed, infested neighborhood trees) depositing eggs on the treated trees.  Remember that ALast Call@ doesn’t harm the females, just the males.  ALast Call@ may become available to home gardeners in Washington as early as this year, but some regular pesticide applications will probably still be necessary to adequately control codling moth when it=s being used.

One New Produce Provides Some Control

Spinosad is another new insecticide product.  It=s made from two spinosyns.  Spinosyns are naturally derived chemicals with insecticidal activity.  The spinosyns were supposedly discovered in 1982 by a scientist who was vacationing in the Caribbean.   The scientist collected soil from an abandoned rum distillery and discovered a new bacteria, named Saccharopolyspora spinosa, in the soil.  (That sounds like an odd vacation even for a scientist.)

This newly discovered bacteria produced metabolites from the fermentation process that were found to have insecticidal properties.   New insecticides, spinosyns, were derived from these metabolites.  The spinosyns act on an insect=s nervous system, causing hyperactivity, paralysis, and death in a relatively short amount of time.  It sounds a bit gruesome, but they=re very effective on some insects and they have extremely low toxicity to humans and animals.  Spinosad, formulated in 1988,  kills a variety of pests, including codling moth, but doesn=t harm many beneficial insects.  Spinosad provides moderately good control of codling moth on apples, but does not provide adequate protection when infestations are heavy.

How about Traps?

If you open a garden supply catalog you may see insect traps recommended for control of codling moth or cherry fruit fly.  These traps really only help tell you when these pests have emerged and help you in timing any control spray applications.  Traps for codling moth only attract the male moths, leaving fertile females to lay their eggs without impunity.  Yellow sticky traps catch both male and female cherry fruit flies, but they only trap some of the flies.  The don=t catch the majority of flies and are not effective controls. 

The Bad News

The bad news is that there are fewer and fewer tools available to home gardeners for controlling codling moth satisfactorily.  While there are some newer, less toxic materials and methods available now and on the horizon, they currently don=t promise to totally prevent damage from infestations.  If planting a fruiting apple, crabapple, pear, or cherry tree, one might even want to ask if it=s worth the trouble... considering the difficulty, time and expense involved in controlling these pests.


Avoid Spreading Disease by Pruning

Avoid Spreading Disease by Pruning

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

What’s your favorite type of pruning tool... a pair of ratchet hand pruners, a lightweight pair of loppers, or a handy folding pruning saw?  Tools like these are standard equipment for gardeners who have a lot of trees and shrubs in their landscape.  They’re needed to prune off ill-placed branches, remove older wood, and eliminate any dead or diseased portions of a plant.  Removal of these infected tissues is very important in preventing the spread of disease.  However, many of us home gardeners may actually be spreading disease if we’re not disinfecting our pruning tools between cuts.

How can pruning tools spread disease?  According to WSU Plant Pathologist, Dr. Warren Copes, if you cut through a section of stem where a pathogen, such as a virus, bacteria, or fungus is present, then the parts of the pathogen may adhere to your pruning tool. When certain diseases are suspected, it’s a good idea to disinfect your pruning tools after every cut.

Copes also points out that not every dead branch is the result of an infection by a disease.  There are also cultural and environmental problems that can lead to dieback.  Let’s look at some common diseases that cause problems in our area and the “protocol” suggested for disease management through pruning and disinfecting the tools we use.

When we have cool, wet springs, a common problem in this area is sycamore anthracnose, also known as sycamore “blight.” True to its name it attacks sycamore trees.  This fungus disease causes cankers or lesions, which eventually girdle a stem and lead to the death of tissues beyond the canker. Over time, repeated infections create sycamores with unsightly crowns.

Where practical, it’s recommended to prune out the cankers caused by the anthracnose fungus.  This improves a tree’s appearance and more importantly removes a source of future infections.  Cuts should be made four inches below any discolored wood.  The disease is spread primarily by wind and rain, not by pruning equipment.  With this disease, you don’t need to disinfect pruning tools after cutting off infected tissue.

One fungus disease that we’ve seen quite a bit of this year is verticillium wilt fungus.  Unlike sycamore anthracnose, verticillium wilt is distributed within a plant at considerable distances from the area of obvious dieback.  It usually enters the plant by way of the root system and moves through the vascular system to plant tissues.  Dieback of branches and limbs is caused by impairment of the root system and the plugging of the vascular system... the system that transports water and nutrients within the tree.  In our region, verticillium wilt is a common problem on maple, ash, sumac, redbud, catalpa, Russian olive, and smoketree. However, there are many other types of trees, shrubs, and garden plants susceptible to verticillium wilt.

While the verticillium wilt fungus can travel throughout a tree, it’s usually not evenly distributed in the plant.  Copes points out, “Since the pathogen isn’t evenly distributed, it’s difficult to identify where the pathogen would be located and also why the fungus is not always spread on pruning tools.”  Dead portions of trees infected with verticillium should be pruned out, but we must keep in mind that this doesn’t remove the pathogen which is located in the roots.  Pruning tools used on trees that have been diagnosed with verticillium wilt or are suspected to have it, should be disinfected between trees and when you are done pruning.

Some “blights” or diseases are caused by a bacterium rather than a fungus.  The most common one that can cause problems in local landscapes is fireblight,  Erwinia amylovora.  Fireblight attacks many members of the rose family including apple, flowering crabapple, pear, pyracantha, hawthorn, cotoneaster, quince, and mountain ash.

Symptoms of a fireblight infection usually start in the spring with infected flowers appearing water soaked.  The flowers may turn brown to black and fail to fall from the tree or shrub.  The bacteria moves down the infected blossom into the twigs, resulting in the sudden death of other flowers and fruits on the same twig.  Often, the twigs will develop a hooked tip or"shepherd’s crook."  Twigs and leaves look almost black, as if scorched by fire.  As the bacteria moves down a twig into a branch, the tissues darken and die. If the outer bark is cut or peeled away, the inner tissues will appear red and water‑soaked.

Fireblight infections commonly occur in the spring when bacterial strands from dead infected tissues are splashed to flowers by rainfall or irrigation water.  The bacteria may also be spread to the flowers by insects that have visited infected plants.  Fireblight often enters a plant through natural openings in the floral parts.

Infection is favored by wet weather and temperatures between 65 and 86 degrees Fahrenheit.  Because of the relatively low rainfall conditions in this region, fireblight is not often a problem in home landscapes.  However, in some years the spring moisture and temperature conditions are just right.  This past spring’s weather provided perfect conditions for fireblight infections in a number of home landscapes.

Once an infection is noted in a plant, it’s important to prune it out immediately.  Pruning cuts should be made at least 12 inches below any discolored wood.  This is because discoloration is a chemical response by the infected plant.  It takes a while before the discoloration forms in infected wood. 

This rule of pruning at least 12 inches below discolored wood can cause a dilemma.  Copes notes that, “Sometimes, a blighted twig or spur may be less than 12 inches away from a larger limb and such removal would disfigure the tree.  In this case, there is no easy answer. Removing the scaffold limb may be necessary.”  If you don’t remove the limb, you should monitor the tree to see if the disease is still present.  While 12 inches is the rule, the disease doesn’t always follow the rules.  It may be present further down, especially if there is a length of time from the first appearance of symptoms and the removal of infected wood.

Pathologists have not been able to confirm that contaminated pruning tools actually spread fireblight from one plant to another.  However, the accepted practice when pruning off fireblight infected wood is to disinfect pruning tools after each cut.

Now we’ve talked about when you should disinfect your pruning tools, but just how should the tools be disinfected?  Plant professionals use a variety of materials to disinfect their pruning tools including commercial horticulture products and also other chemicals.  An article on disinfecting horticultural tools is available from University of Florida IFAS Extension at:

Be aware that some disinfecting chemicals are corrosive.  Make sure to wash the chemical off after the final disinfecting, allow the equipment to dry thoroughly, and then coat the metal parts with light oil or a silicone based spray.  If viruses are the suspected disease, clean your tools by washing them with detergent to physically remove the virus and inactivate virus that may remain on the blades.


Cold Temperatures Can Damage Plants

Cold Temperatures Can Damage Plants

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent

How cold can it get before plants suffer cold temperature injury? It’s important to keep in mind that a plant’s potential hardiness is genetically determined.  Plants that are native to a geographic region have evolved in response to that area’s climate and weather patterns.  It can be thought of as “survival of the fittest”... the hardy plants that can survive the winter weather of a region produce offspring that are also hardy.  Through this natural selection process, native plants are usually able to survive the winter cold of their particular native region.

However, a hardy plant in the middle of summer can’t withstand the same amount of cold that it can in mid-winter.  This is because hardiness to cold develops as a series of physiological changes within the plants.  The first change to occur is a response to the shortening days of late summer and early fall.  Plant hormones are produced in response to the shorter days.  These tell the plant that winter is coming and plant tissues develop greater resistance to damage from freezing temperatures. 

As fall proceeds and temperatures become increasingly cooler, the plants develop even greater hardiness.  The rate at which plants develop hardiness varies from species to species.  The rate also is dependent on the degree of cooling that occurs in the fall.  If fall temperatures remain mild, plants may fail to acclimate fully to cold temperatures.  Because our late fall and early winter has been so mild, it’s very possible that some plants sustained some cold temperature damage from the recent deep freeze. 

At some time in the middle of winter, plants develop their ultimate mid-winter hardiness.  This point is genetically determined.  It’s interesting to note the part that genetics and geographics play in plant hardiness.  The ultimate mid-winter hardiness can be quite variable even within the same species.  For example, Douglas firs that evolved in the Rocky Mountains are hardier than Douglas firs that evolved in the Cascades.  Similarly, a flowering dogwood that is native to the New York state region is hardier than one from the Florida or Georgia regions.  In both cases the plants are exactly the same genus and species, they just evolved in a different climatic region.

After the plants receive their ultimate mid-winter hardiness they begin to deacclimate or lose some of their hardiness.  Like the acclimation process, deacclimation is usually gradual.  However, deacclimation can occur quite rapidly during an extended warm spell.  Plants have the potential to acclimate to colder temperatures again and again when temperatures drop, but they lose this potential as spring approaches and growth begins.

Many gardeners ask how they can protect their plants from cold temperatures.  Plants aren’t “warm blooded” creatures.  Putting blankets around a tree trunk won’t keep them warm.  Blankets can’t help, but other things can be done to provide a measure of protection:

  1. Select plants that are hardy for the local climate.  Nurserymen will indicate a plant’s hardiness by noting the USDA hardiness zones for which it’s suitable.  The zone for the Tri-Cities area is Zone 6.  Gardeners close to the river or in the Walla Walla area might be able to push it to Zone 7.  You may see “borderline hardy” plants in area landscapes that do well here for several years when the winters are relatively mild winters, but then they succumb to a particularly cold winter.  That’s because they’re not truly hardy for this area.
  2. When planting conifers (evergreens) in the landscape, situate them to limit their exposure to sun and wind.  If you live in a particularly exposed location where there is no “protected location,” plant a windbreak to protect them in winter months.
  3. Keep plants in a healthy condition.  Healthy plants are better able to withstand the rigors of winter.  Stressed plants are more susceptible to winter injury.
  4. Plants that are actively growing late in the season fail to acclimate as winter approaches.  Avoid fertilizing, pruning, or irrigating excessively towards the end of the summer and in early fall.  Keep in mind that the fall fertilizer that you put on the lawn may well be reaching tree roots and encouraging late season growth.  Try to avoid fertilizing trees and shrubs in the fall, especially those that are not extremely winter hardy or ones prone to winter injury.
  5. While you don’t want to water plants excessively and encourage late season growth, it’s also important to note that water stressed plants are less hardy.  Don’t let your plants go into winter with dry soil.
  6. Mulch the roots and crowns of tender plants, plants prone to winter injury, and recently planted trees, shrubs, and perennials.  Use loose mulch, such as finely shredded bark, that won’t mat down or exclude air from the roots.  Roses will usually benefit from an application of bark to the crown to protect them from cold and dessicating winds.
  7. Protect the trunks from sunscald.  Sunscald damage happens when bark surfaces on the south and west sides of a tree are warmed by bright winter sun and then the temperature drops rapidly when the sun goes down.  This abrupt temperature change can damage the bark and cambium underneath.  Newly planted trees; trees with dark bark, such as cherries; or young trees with thin bark, such as maples, ash, crab apples, and tulip trees are particularly susceptible to this type of injury.  Wrap the tree trunk with a commercial trunk wrap or paint it with an inexpensive interior white latex paint to reflect the sun and prevent damage.  Bark wraps should be removed in the spring.


Managing Mite Problems

Managing Mite Problems

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

It might be mites, it might not.  Spider mites are often blamed for plants turning brown evenwhen they=re nowhere to be found on a failing plant.  How can you tell if your tree, shrub or garden plant has mites? 

What are Mites?

Spider mites are not insects.  They=re tiny arachnids related to the other arachnids that we know and Alove@, includingspiders, ticks, and harvestmen (daddy longlegs).  Like their relatives, spider mites have eight legs and lack wings, antennae and compound eyes.  Members of the insect family typically have six legs, antennae, compound eyes and wings.

Spider mites are visible, but extremely small (1/60th of an inch in length or smaller) and almost microscopic. One way to tell if a plant has mites is to tap a branch or some leaves suspected of having mites over a piece of white paper.  Invariably, little dust specks will fall onto the paper.  If after a second or two the little specks start crawling, it=s a good bet that they=re mites.

The other way to detect a mite problem is to look for their damage and other signs of their presence.  Spider mites don=t have chewing or piercing-sucking mouthparts. To access plant sap they pierce and rupture leaf cells with needle-like stylets.  They then suck up sap that seeps out of the punctured cells. This type of damage leads to the death of individual cells, giving the leaf a finely stippled appearance. As the damage increases a leaf appears discolored, then it turns yellow to brown and dies.  Some types of mites even inject a toxin when they feed which can lead to leaf distortion.

Another sign of a mite infestation is webbing.  The webbing is very fine and, depending on the type of mite, is often found on the undersides of leaves.  It shouldn=t be confused with more visible webbing made by spiders or the cottony masses from cottonwood and poplar trees.  However, it=s important to note that not all spider mites produce webbing... so you can have a mite infestation without webbing.

Mite Life Cycle

Knowing the life cycle and habits of a pest enables us to better manage that pest when it becomes a problem.  Because the two-spotted mite is the most common spider mite that causes problems for trees, shrubs, garden flowers, and vegetables let=s take a look at its way of life. 

The two-spotted spider mite, thus named because of the two dark spots on the back of the adult mite, start out as an egg.  The egg hatches into a larva that has only six legs.  This larva molts into a nymph with eight legs. The nymph molts into a larger nymph and then becomes an adult.  Both the larva and the nymphs resemble the adult.  This entire process takes about five to 20 days depending on the weather.  When winter comes, many types of mites overwinter as eggs. However, the two-spotted mite overwinters as an adult in the soil or in bark crevices on trees and shrubs.  They become active as soon as plant growth begins in the spring.

Mite Build-Up

During hot weather, two-spotted mite populations can build up quite quickly causing plant damage.  A female two-spotted spider mite lives approximately 30 days and lays about 100 eggs. One reason that hot weather leads to spider mite explosions is because of the low humidity.  With low humidity the excess water they excrete evaporates more rapidly.  This allows them to feed more heavily, favoring reproduction.  Another factor is that many of the natural mite predators are stressed by the hot, dry conditions and aren=t able to multiply quickly enough to keep up with the burgeoning mite population.

Hot weather doesn’t=t favor all types of mites. One very notable exception is the spruce spider mite that feeds on conifers, especially spruce and juniper.  This mite is most active during cooler spring and fall weather and actually goes dormant (in an egg stage) during hot summer weather.

Natural Mite Control

Spider mites do have some natural enemies.  They=re Adinner@ for predatory insects, such as dark- colored lady beetles, lacewings, predatory thrips, minute pirate bugs, and big-eyed bugs.  There are also a number of predatory mites that feed on spider mites and keep their populations under control especially when the weather isn=t extremely hot and dry.  One reason for spider mite outbreaks when the weather is not hot is that these predatory mites are killed off when insecticides are applied to plants.  They=re particularly sensitive to carbaryl (Sevin), but may also be harmed by other insecticides.   To keep spider mites in check, avoid using pesticides that kill off predators.

Controlling Mite Infestations

One cultural technique that helps keep mite populations in check is periodically syringing mite-prone plants with a forceful spray of water.  This forceful spray not only knocks off and kills the spider mites, but also dislodges the webbing that collects dusts and deters the natural predators.  It=s also important to keep plants from becoming drought stressed in hot weather.  Plants under stress are more vulnerable to spider mite attack.

If cultural controls don=t work, then pesticide sprays may be needed if significant damage is showing up on your plants.  Since mites aren’t=t insects, most garden insecticides are not very effective.  There are specific miticide chemicals for mite control, but they=re not readily available to home gardeners.  Two options that are available are insecticidal soaps and horticultural oils.

Insecticidal soaps are only moderately effective against mites.  For best results good coverage to both the upper and lower leaf surfaces is essential.  (Remember most mites are on the bottom of the leaves.)  The soap is only effective on the mites that are contacted with the soap spray.  Eggs are not harmed, so repeat applications are usually needed within seven to ten days in hot weather. Additional retreatments may be needed. 

During the growing season horticultural oils may be applied at the summer rate... but be sure to check the label for any hot weather precautions.  Horticultural oils may also be used on dormant plants in the spring at a dormant application rate for controlling overwintering adult mites and mite eggs. 

Spider mite infestations are not as common as some gardeners think.  I sometimes see infestations of spider mites on willows, marigolds, roses, and impatiens.  Spruce spider mites are occasionally a problem on area junipers and spruce, especially dwarf Alberta spruce.  I very seldom see spider mites on arborvitae or other landscape and garden plants.  So if your plants start to turn brown, check for stippling, crawling specks of dust, and very fine webbing on the undersides of leaves.  If in doubt, take a sample to your local Master Gardener Plant Clinic



Trees with Something Special

Trees with Something Special

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

Not all trees are the same.  There are some trees with that “something special” that makes you want to plant them in your yard.  It might be beautiful flowers in the spring or summer, a different shape or overall form, brilliant color in the fall, or even outstanding bark.

When you plant trees and shrubs in your landscape, you’re painting a picture.  Good landscape designers, photographers, and artists all know that there should be a focal point in a picture.  The focal point directs the viewer where to look, creating a sense of depth and space. In landscape designs that focal point is often a tree with that “something special”.  Other landscape plants are used for balance and harmony in the picture.  No picture or front landscape design should have two focal points at one time.  It’s unsettling to the eye and creates disharmony.

In formal landscapes the focal point is often centered with the other elements of the design placed symmetrically to the left and right, mirroring each other.  While it’s easy to balance these types of landscape designs, they tend to be stiff and lack originality.  However, they work well with very formal styles of architecture. 

Asymmetrical landscape designs are informal and have more room for creativity and diversity in plant selection. Focal points are positioned off-center and other plants are carefully selected and placed to create balance.  Most home landscape designs are asymmetrical informal designs.

Knowing that the tree you plant with “something special” will be the focal point of your landscape, special care should be taken with its selection.  It’s easy to fall in love with a tree at the nursery or in a catalog, but you also need to make sure it’s suitable for your design and landscape conditions.  Here are some questions you should ask before planting a tree with something special.

What’s the Mature Size?

Find out its ultimate mature size.  It may look small and cute in the nursery, but just how big will it be when it grows up?  Will it fit where you want to put it in your design?  A focal point tree can grow to a size that’s out of balance with the rest of the landscape.

Is it Hardy Here?

Is it hardy in this region?   This region is generally considered to be located in Zone 6 on the USDA Hardiness Map. Plants hardy in Zones 7 or higher may grow well and survive our milder winters, only to die several years or more after planting when we experience colder winter temperatures that can be expected from time to time in this region.

Is it Suitable for Our Climate and Soils?

Will it withstand local soil and climate conditions? Most home landscape soils in this region are somewhat to very alkaline.  Some trees prefer acid soils rich in organic matter.  If a plant has to struggle to grow, it won’t likely become the attractive focal point you had anticipated.

Are there Any Troublesome Insect or Disease Problems?

Does it have any major pest or disease problems that could lead to continual maintenance problems or a short life expectancy?  A sick plant detracts from the landscape “picture” and may well be an unattractive focal point.

Is Suitable for the Site & Exposure?

Does your design meet the tree’s exposure needs?  Does it need protection from full exposure to sun and wind?  Does it need full sun or partial shade?  Select a tree suitable for the location where it will be planted.

Does It Create A Mess?

Does it create a litter problem with leaves, seed pods, fruit, or flowers?  If you want your landscape to be as “pretty as picture”, a tree that creates a lot of litter can detract from the picture you have created.

There are many trees available from local garden centers, nurseries, and mail-order catalogs that might catch your eye as that tree with some special characteristic that makes you want to take it home and use it as a focal point in your landscape design.  Here are a some trees you might run across on your search.

Weeping Trees

Weeping trees have a pendulous form that contrasts with the many other upright and spreading forms in a landscape design.  Their graceful hanging branches are poetry in motion.  There are both large and small weeping trees... be sure you know how tall and how wide the weeping tree you select will grow.

Double Weeping Cherry (Prunus subhirtella ‘Pendula Plena Rosea’) (25' x 25'). In addition to a graceful weeping form, the multi-seasonal interest of double pink flowers in the spring and yellow to bronze leaf color in the fall make this tree a wonderful focal point specimen.  This species of flowering cherry is longer-lived,  hardier and more heat and stress tolerant than many of the other flowering cherry species.  Two other weeping cherries are also worth consideration.  Weeping Yoshino Cherry (Prunus x yeodensis ‘Shidare Yoshino’) (12' x 15') with pink tinged white flowers and Snow Fountains Cherry (Prunus x ‘Snofozam’(12' x 12') with white flowers are smaller, but equally as graceful weeping flowering cherries.

Weeping Katsura Tree (Cercidiphyllum japonicum ‘Pendulum’) (25+’ x 20') Katsura trees are one of the most beautiful trees you can plant, especially in the weeping form.  The heart-shaped leaves are bluish-green during the summer and turn an outstanding yellow-orange in the fall.  The branches cascade to the ground evocative of a waterfall.  The bark of this tree is susceptible to sunburn if drought stressed or planted in high heat situations.

Young’s Weeping Birch (Betula pendula ‘Youngii’) (15' x 20') Many gardeners can’t resist a birch, especially one with white bark.  This weeping form is perfect as a focal point for gardeners with smaller landscapes that must have a birch.  It tends to grow asymmetrically giving it an interesting overall form.  It’s often grafted onto a standard stem creating a “mop-head” type of appearance.  Gardeners should be aware that it is susceptible to the bronze birch borer that decimates birch trees and is a serious problem in this region.

Weeping Beech (Fagus sylvatica ‘Pendula’) (50' x 60+') A large weeping tree that has an ascending trunk and is slow growing.  Weeping Purple Beech (Fagus sylvatica ‘Purpurea Pendula’) (10' x 15') is a much smaller tree with purple leaves and a dome-like crown.

Other weeping trees to consider include Emerald Cascade Honeylocust ‘Emerald Cascade’ (16' x 16') a honeylocust with dark green, fine textured leaves that turn butter-yellow in the fall; Chaparral Weeping Mulberry (Morus alba ‘Chaparral’) (12' x 16') a non-fruiting mulberry that’stolerant of heat and alkaline soils; Weeping Pagoda Tree (Sophora japonica ‘Pendula’) (15' - 25' x 15') unlike the species it produces few flowers; and Weeping Willowleaf Pear (Pyrus salicifolia ‘Pendula’) (15' x15') a weeping pear with gray-green, willow-like leaves.  There are also numerous glorious weeping crab apple trees, but they should not be grown here because they can become infested with codling moth and require regular spraying to help protect local commercial apple orchards.

Flowering Trees

Flowers, especially early spring flowers, can lead to love at first sight when the trees are in bloom.  However, blooms don’t last very long and it’s advisable that the tree have other characteristics that will make it the focal point of your design at other times during the year... such as fruit, fall leaf color, form, texture, or bark characteristics. The list of noteworthy flowering trees is very long. Here are a few you might want to consider.

Mt. Fuji Cherry (Prunus serrulata ‘Shirotae’) (15' x 20') You can’t wrong with a Japanese flowering cherry.  This one has a spreading form and pink flower buds that open to large double white flowers.

Kwanzan Cherry (Prunus serrulata ‘Kwanzan’) (30' x 20') The most popular of the double flower types of Japanese cherry.  It has rosy pink flowers borne in clusters, plus the leaves turn a nice bronze to orange color in the fall.  A very showy tree, but it’s susceptible to borers and cankers.

Vossii Goldenchain Tree (Laburnum x watereri ‘Vossii’) ( 25' x 20') This tree has an interesting vase shape and produces a spectacular display of rich yellow flowers in hanging clusters.  However, the tree is not very attractive when it’s not in bloom. Beware, the seeds are poisonous. 

Flowering Dogwood (Cornus florida) There are many cultivated varieties of flowering dogwood and hybrids with kousa dogwood or the Pacific dogwood.  The flowers range from pure white to creamy white to pink, deep pink, and ruby red.  The shape and size also vary from cultivar to cultivar, but all are relatively small trees less than 25 feet tall.  Flowering dogwoods prefer soil that is high in organic matter and acidic.  While these conditions are not found in most area landscapes, the trees will do quite well here if provided with adequate moisture, acidifying fertilizer, and organic mulch.  Many local gardeners find that flowering dogwoods perform best in a protected location and need pampering for the first several years before they become well established.

There are many other flowering trees, but none so durable and versatile as flowering crab apple trees and the flowering pears.  However, they’re not recommended for local landscapes because of the problem with codling moth.

Trees with Attractive Fall Color, Bark, or Leaves

As the growing season ends, the fall color of the leaves, the silhouette of the tree,  and the pattern of the bark are all characteristics that can maintain a tree’s position as a focal point. 

Here are some more trees to consider for fall color, form, or bark characteristics:

Red Maple (Acer rubrum) (40' -  45') The true red maples (not to be confused with Norway maples with purple leaves) just can’t be beat for their riotous display of brilliant orange to bright red leaves in the fall.  October Glory, Red Sunset, and Autumn Flame have some of the best fall color you can find.  October Glory is better adapted to areas like ours with hot summer temperatures.  During the spring and summer the leaves of red maple are green.

Empress Tree (Paulownia tomentosa) (40 '- 50' x 40' - 50') While this is a large, very messy tree, many gardeners who see it fall in love with its unique form, flowers, big leaves, and large seed capsules.  It’s a coarse tree with a dense rounded crown.  The pale violet flowers are produced in May.  In the fall the tree is covered with unique one to two inch persistent capsules.

Heritage River Birch (Betula nigra ‘Cully’) (40' x 30') Many local white-barked birches are succumbing to bronze birch borer, so if local gardeners want to grow a birch with interesting bark, this is one to try.  The peeling bark is a mottled mosaic of cream, orange, and tan colors. The leaves are large, glossy, and light green. 

Red Oak (Quercus rubra) (50' x 45') If you want an oak, pick this one. It tolerates local alkaline soil conditions and grows relatively fast, plus it’s dark green leaves turn a beautiful rich red in the fall.  This is a bit large as a focal point tree, but worth considering for larger homes and landscapes. 

RotundilobaSweetgum (Liquidambar styraciflua ‘Rotundiloba’) (45' x 25') If you’re looking for good fall color, the sweetgum will deliver.   The fall colors of the different cultivars range from spectacular burgundy red to orange to purple.  Rotundiloba has bright green glossy leaves with distinctive rounded lobes and it’s also fruitless.

Japanese Maple (Acer palmatum) The Japanese maple is a prized maple for creating focal points, especially in smaller yards.  This much appreciated and valued tree varies greatly in mature size and form.  While there are many weeping forms, there are also numerous upright cultivars.  Summer leaf colors vary from green to purple to red.  Many forms have lacy leaves.  Japanese maples are lovely specimen trees, but most won’t tolerate dry soil, low humidity, wind, intense sun, and high temperatures.  In this region Japanese maples need to be placed in a protected location, away from wind and hot afternoon sun.  They should be mulched with organic mulch and the soil must be kept moderately moist.


Trees to Avoid

Trees to Avoid
(Trees Which Are Often Used, But Have Serious Insect, Disease, Or Litter Problems)

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

SYCAMORE (Platanus occidentalis) 75-100'. A very large tree which should not be planted except on the largest lots. Constantly dropping leaves, twigs, and seed clusters. Sycamore blight (anthracnose) is a serious disease problem. It appears to be very sensitive to injury from the herbicides 2,4-D and dicamba, even when used properly.

TREE OF HEAVEN (Ailanthus altissima) 40-60". This tree is adaptable to the most difficult of conditions but it is a course tree that tends to be very weedy. Should be planted only in impossible situations where nothing else survives.

SILVER MAPLE (Acer saccharinum) 50-120'. Another very large tree with a fast rate of growth. It tends to be a very weak wooded subject to many disease and insect problems. There are many superior forms of maple with many more desirable aspects. Has very little fall color. Roots are very invasive.

BOX ELDER (Acer negundo) 30-50'. This is another fast growing, weak wooded maple. It tends to be susceptible to many disease and insect problems. Very susceptible to verticillium wilt. The white variegated form has some merit. Short-lived tree.

POPLAR (Populus alba) 40-90'. This is an easy to grow "trashy" tree that continually drops leaves, twigs, and other debris. It is weak-wooded and tends to be weedy. Susceptible to many diseases and wood borers. Short-lived tree. Water seeker, invasive roots.

COTTONWOOD (Populus deltoides) 75-100'. Very large tree with all the problems of the preceding poplar. Water seeker, invasive roots.

PIN OAK (Quercus palustris) 60-70'. This is a good tree although there are many better oaks available, but it is intolerant of the alkaline soils encountered in this area.

WEEPING WILLOW (Salix sp.) 50-80'. A well loved tree but out of place in the normal home landscape. It is extremely weak wooded and very susceptible to aphids. The root system is very invasive.

RUSSIAN OLIVE (Elaeagnus angustifolia) 15-40'. Not the most beautiful of trees, but has a purpose in saline soils or where gray foliage is desired. It tends to be a rangy, weedy plant. Very susceptible to verticillium wilt, crown gall and aphids.

SIBERIAN ELM (Ulmus pumila) 50-70'. Does not deserve to be planted in the landscape. A shrubby tree with poor form. Brittle wood. Very susceptible to insects - especially aphids and the elm leaf beetle.

CRAB APPLE (Malus sp.) Crabapples are very nice trees but their fruit, large or small, are attacked by codling moth and apple maggot. Because these pests cause problems for local commercial apple growers, it’s not recommended to grow them in this region unless you intend to spray regularly with recommended pesticides to control these pests. In fact, it’s county law that you control these pests or remove your tree.

LAVELLE HAWTHORNE (Crataegus lavellei) 20-30'. A nice tree with lustrous deep green foliage and white showy flowers, but also should not be grown because it’s fruit are attacked by codling moth and apple maggot.

Early Fall Cold Snap Can Lead to Damage on Landscape Plants

Early Fall Cold Snap Can Lead to Damage on Landscape Plants

Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent  

In our area we typically have relatively long periods of mild fall before we finally get a hard freeze.  In most years, the leaves senesce and normally fall off the tree as leaves do in autumn.  However, occasionally an early cold snap will take us and our trees and shrubs by surprise.  One very obvious sign of the sudden end to the growing season is all the leaves left hanging on the trees.  Just like us, they weren’t ready for the severe cold.  They didn’t have time to form the “abscission layer” that develops at the base of the leaf stem and causes the leaf to fall. The leaves stay attached to the trees.  This is a common trait of trees such as oaks, but unusual for many other trees and shrubs.  Some of these leaves will hang on for most of the winter, but others will fall every time we have a strong windy day. All will drop off by spring when the new leaves start to develop.

How Plants Get Ready for Cold Winter Temperatures

While these persistent leaves are not harmful to the plants, they are a sign that many trees and shrubs were not ready for record breaking severe cold temperatures.  Plants go through a physiological process to be able to avoid damage from cold temperatures.  This begins in late summer and early fall as the days grow shorter and the temperatures begin to decline.  Plant hormones formed in response to these changes trigger the cessation of plant growth, stimulate the formation of the abscission layer, and bring about physiological changes that allow the plant to withstand colder and colder temperatures.  In response to gradually cooling temperatures, the plant attains its winter hardiness through this physiological process called “hardening” or “acclimatization”.  By midwinter it has attained its ultimate hardiness, which is genetically determined.

The potential problem caused by our recent record-breaking cold spell is that many plants were not fully acclimated and hadn’t achieved their ultimate winter hardiness.  While they might be able to withstand 15 degrees, 10 degrees, or even 5 degrees in mid-winter, they may have sustained damage with the cold temperatures coming so early.  It won’t be until the next spring and summer that the amount of potential damage can be assessed.

Symptoms of Damage

For gardeners, the next spring and summer are the “moment of truth” for appraising the extent of possible damage.  The first clue that damage actually occurred will be the failure of a plant to leaf out and grow.  In some cases, leaves may form while flowers fail to develop because of injury.  There may also be plants that die abruptly after appearing unscathed with leaves and flowers growing normally.  On these plants, the buds were not injured but stem and branch tissues were severely damaged or killed.

When cold is sudden and sustained over a period of several days, roots of plants also may be damaged.  This usually takes longer, perhaps several months or more, to become evident on established plants.  Symptoms include outright plant death or gradual thinning and dieback of the crown.

Help for Injured Plants

Once spring arrives, there are some things gardeners can do to help an injured plants. First, be patient. Wait until late spring, after there has been sufficient time for the plants to fully leaf out, and then prune out dead wood.  Be sure to prune properly.  Don’t make stub cuts.  Prune back to a bud, stem or trunk with live green healthy wood.  Only remove dead and severely damaged wood.  Follow that with tender-loving care, proper watering, and mulching to retain soil moisture.  Injured plants are already stressed; so don’t add to their stress. 

Experts disagree about fertilizing winter-injured plants.  Some advise against it, others recommend it. One thing you don’t want to do is encourage excessive growth with heavy fertilization because injured roots and transport tissues may not be able to support this growth.  I recommend watering properly and fertilizing only lightly in the spring.

Minimizing Cold Temperature Damage

There’s not much we can do to protect our plants from record-breaking low temperatures in the fall or winter.  But we can minimize losses to our landscape and gardens by selecting plants hardy to our region.  Many landscape plants that we commonly use are “exotics” and are better adapted to climates where they’re considered natives.  Exotic plants respond differently to local climatic clues than do native plants.  Native plants have a greater chance of surviving winter cold temperatures.  However, gardeners like to test the limits and try growing many different plants... so even if we are planting “exotic” trees, shrubs, and perennials, we should make sure they’re hardy for our zone.

Several late-season gardening practices can help plants avoid winter injury, whether they’re natives or exotics.   It’s important not to promote late-season growth. Avoid fertilizing trees, shrubs, and perennials late in the growing season.  Don’t prune plants late in the growing season.  Wait for trees and shrubs to become fully dormant.  Late winter is the best time to prune.  Don’t drought stress your plants, but do cut back on the watering as the weather cools.  They certainly don’t need as much water in late summer and early fall as they did during 100-degree heat.  (It’s still important though not to drought stress your plants, especially needled and broad-leaved evergreens, as they go into winter.)

Why Sycamores Aren’t a Good Shade Tree for Most Home Landscapes

Why Sycamores Aren’t a Good Shade Tree for Most Home Landscapes

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

The “true” sycamore is Plantanus occidentalis.  It’s also known as the American Planetree, Buttonwood, and Buttonball Tree.  This tree is native to North America.  It grows to a height of 75 to 100 feet.  Behemoth would be a good description of mature sycamores.  Sycamores are extremely susceptible to sycamore anthracnose (blight) and are also subject to problems with powdery mildew and sycamore lace bug. 

The London planetree (Plantanus x acerifolia) is commonly referred to as a “sycamore” in this our area, but it’s actually a different species.  It’s a result from a cross between the American sycamore (Plantanus occidentalis) and the Oriental planetree (Plantanus orientalis).  This London planetree is also excessively large, growing to a height of 70 to 100 feet.  This species is more resistant to sycamore anthracnose, but is still subject to the disease along with powdery mildew, sycamore lacebug, and the American plum borer.  There are several newer cultivars of the London planetree which are more resistant to anthracnose and should be considered when anyone decides to plant a sycamore.  

What’s good about the London planetree?  It’s a fast growing shade tree.  Unlike many other fast-growing shade trees, it’s not extremely weak wooded and thus isn’t prone to a lot of limb breakage in ice and snowstorms.  It’s easily transplanted and will do well in most soils, but prefers a deep, rich soil. It’s also tolerant of city conditions... air pollution, compacted soils, and drought.  It’s a very durable tree.  As a big tree, it also provides lots of wonderful shade in parks. 

Probably the most attractive feature of the tree is its bark.  As the tree matures, it sloughs or sheds pieces of the outer bark, giving it an interesting dappled pattern of olive green, cream, and light brown.   This random mosaic pattern is quite lovely and gives a special interest to the tree in winter.  If I was going to like the sycamore, it would be for its eye-catching bark. 

Now... on to it’s less desirable features.  One of the most obvious negative features is the size of the tree.  The London planetree is a BIG tree!  It grows to gargantuan proportions and is not well suited to the typical home lot or along a city street.  Growing to at least 70 feet or more in height and 80 feet or more in width, you need plenty of room for a London planetree.  Planted in the wrong place it can quickly come into conflict with utility wires, sidewalks, and driveways. Keep in mind that roots go out at least as far out from the tree as the tree is tall ... or more.

Because of its size and the lack of forethought when planting this tree, many tree owners opt to butcher their “sycamore” with topping or severe pruning when it gets too large for its space.  This pruning shortens the life of the tree and results in lots oftwiggy growth.  Attachment of this growth is weak, creating a hazard as the resulting branches grow larger and heavier.  Numerous fallen branches are often the consequence of windstorms and past topping of the tree. Open topping wounds lead to eventual wood rot.

Another problem with sycamores are their susceptibility to sycamore anthracnose , also known as sycamore blight.  This is a fungus disease that attacks sycamore buds, leaves, and shoots. The most typical symptoms are small to large brown dead areas along the main veins of leaves. Severe infections lead to leaf drop.  Infections in twigs and branches cause twig dieback. 

Cool, wet springtime conditions favor anthracnose development on sycamore. The disease is more severe when we experience a spring like we encountered this past April and May.  While it’s not “normal” for us to have repeated precipitation during the spring, it seems to be a frequently occurring weather pattern during the past five to ten years.  A disease that shouldn’t ordinarily be a problem with our “normal” climate, has continued to attack and disfigure area sycamores.  Repeated attacks seldom kill a tree, but they can sure give it a rather ugly, witches-broom or bushy appearance.

Fungicide applications to control the disease can be made early in the season when the buds swell and again when the bud caps begin to break.  However, control is often difficult because of the large size of the tree and the difficulty in getting good coverage. 

Powdery mildew is another disease problem that has been infecting some area sycamores.  It causes a distinctive white powdery fungus on upper leaf surfaces and green shoots. Leaves, especially those at the ends of branches, may be dwarfed, twisted, and completely covered by the fungus. The disease is usually worse on severely pruned trees which have lots of succulent leaf and twig growth. The powdery mildew usually becomes evident in late summer or early autumn.  Little real damage actually occurs to the trees other than the deformity of the leaves.  Control with applications of fungicides is not warranted unless the tree is of very high value or in a location where it serves as a focal point.  

As already mentioned, there are anthracnose resistant cultivars of the London planetree (a.k.a. sycamore.)  One cultivar, `Yarwood’ is very resistant to powdery mildew and fairly resistant to anthracnose.  ‘Bloodgood’ is very resistant to anthracanose.  `Liberty’ and `Columbia’ are two other cultivars that have been touted as being anthracnose resistant, but they’re apparently only resistant to eastern strains of the disease and not western strains. 

One of the positive features of sycamores planted in our area is that they aren’t often attacked by insect pests.  However, one little creature seems to be on the rise.  It’s the sycamore lacebug.  The lacebug is a tiny creature with clear lace-like wings.  It sucks the sap from the undersides of leaves causing astippled or speckled appearance on the top of the leaf.  The lacewings leave shiny black spots of excrement on thelower leaf surface. 

Visible damage from the lacebugs only seems to become evident late in the season.  In most cases it should not seriously harm the trees.  Trees should be kept in a vigorous condition with proper cultural care.  Stressed trees are more susceptible to attack and damage.  It’s especially important not to drought stress the trees during hot weather.  If control with a pesticide application seems necessary, an application of insecticidal soap would provide some control and still protect many of the natural predators.

Finally, this is a messy tree. Because the leaves are so large and numerous, they ’re a real nuisance in the autumn.  Add to this the litter from the numerous seed balls and twigs shed by the tree and you have a persistently messy tree.  In conclusion, it’s not advisable to plant a sycamore... but if you must, plant a resistant cultivar of the London planetree and be sure you have plenty of room for it to grow.