Buying Quality Trees for Planting in Your Landscape

Buying Quality Trees for Planting in Your Landscape

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

Before buying a tree to plant in your landscape, make sure it’s a healthy, high-quality plant.  Whether you shop for your trees and shrubs at a local nursery or at a discount store, you should keep in mind that the plant is not only an investment of money, but also of time.  Don’t waste your time or money on a plant that will not grow well or will become a liability with time.

Some bargains aren’t really a bargain.  That’s why the International Society of Arboriculture advises, “When you buy a high quality tree, plant it correctly, and treat it properly, you and your tree will benefit greatly in many ways for many years.  When you buy a low quality tree, you and your tree will have many costly problems even if you take great care in planting and maintenance.” The International Society of Arboriculture, or “ISA” for short, is a non-profit organization supporting tree care research and dedicated to the care and preservation of shade and ornamental trees.

So what determines if a tree is high quality or low quality? It’s the condition of the root system, trunk, and framework of branches.  A high quality tree is one with an adequate root system for the tree.  The container should be large enough to accommodate the roots without circling roots forming on the outside of the root ball.  Roots that are circling, kinked, or entwined will continue to grow that way.  This usually leads to future problems when the roots eventually choke or “girdle” each other as they grow.  A few circling roots can be cut with a sharp knife and loosened, but low quality plants with a tight mass of circling woody roots should be avoided.

If a root ball is dug and wrapped in burlap (balled and burlapped) there should be enough of a root system to support the tree.  A rule of thumb used in the nursery industry indicates that the diameter of the root ball should be at least ten to twelve times the diameter of the trunk, as measured six inches above the trunk flare.  The “flare” is the area at the base of the tree trunk that curves outward.  It’s where the roots meet the trunk.  When purchasing a balled and burlapped tree, you should be able to see the flare on the trunk and the top of the root ball should be flat, not mounded and covered with bark.

After you get the tree situated in the planting hole, with the top of the root ball at the same level as it was growing in the nursery, you’ll want to cut all the twine off the ball and carefully pull back the burlap.  Remove the burlap by cutting, being careful not to disturb the soil ball surrounding the roots.   A plant with many major roots crushed, cut, or torn is poor quality.  This will greatly affect the tree’s ability to grow.   A plant is also low quality if it lacks enough roots to help hold the root ball together.  This type of tree will have severely restricted growth too.  However, even a high quality plant may have a few damaged major roots.  Use sharp pruning shears to make clean cuts on the injured roots.

A quality tree will also have a trunk free of wounds that are the result of poor pruning cuts or physical injuries to the bark.  ISA warns that there are often injuries or problems concealed by trunk wraps.  “Never buy a tree without thoroughly checking the trunk.”  Problems include poor pruning cuts that leave stubs that won’t “heal.” These can lead to disease and structural defects.  Older pruning cuts should show a ring of callus tissue that has covered the area of the cut.  These cuts are made just outside what is called the branch collar.  If branches are removed with flush cuts, the wound won’t cover over as quickly and can lead to cankers, trunk cracks, or wood decay.

Trees should also have a good, strong basic framework of branches.  If the framework hasn’t been well developed in the growing nursery, you won’t be able to correct significant structural defects with pruning.  The branches on a tree should be evenly spaced along the central leader.  According to the ISA, trees that have branches that are “squeezed” together should be avoided.  “Squeezed” branches are where you have two main branches or leaders arising from the same point.  As these leaders grow, they “squeeze” each other.  The older and larger the tree gets, these leaders often split apart.  Squeezed branches can’t easily be corrected by pruning, especially the larger a tree becomes.

You also want branches with strong attachments, ones that aren’t “squeezed” to the trunk.  When the angle of attachment between the branch and the trunk is less than 45 degrees, this is considered a weak attachment prone to cracking and breakage.  If you’re buying a fairly large specimen, examine the branches and look for small cracks that may already have formed at their bases.  A small crack can later develop into a larger one and lead to branch breakage.

Let’s review.  When buying a tree... you should look for a one with an adequate, healthy root ball.  The trunk should be free of defects and the branches should be well placed along the trunk.  Trees can be a significant purchase.  Take the time to inspect the tree you’re buying.  Inspect the trunk for defects and assess the branch placement and attachment.

Inspecting the root ball is trickier.  While I know a horticulturist who recommends removing a tree from its container right in the nursery, most nurseries won’t like you doing this.  You certainly can’t look at the roots of a balled and burlapped plant at the nursery without causing all sorts of problems.  I recommend checking the roots immediately when you get the plant home.  It’s easy to check the roots of a container grown tree or shrub.  However, balled and burlapped specimens should first be situated in the planting hole and ready to be planted before removing the burlap. 

Some nurseries will recommend leaving the burlap on the root ball.  They will not guarantee their plants if you remove the material.  However, Mid-Columbia Community Forestry Council members have observed too many problems, such as a lack of roots and severe damage to the root system, beneath the burlap to be comfortable with leaving it on.  The burlap also usually doesn’t rot quickly enough in our climate and frequently restricts root and tree growth.  The fact that burlap is often treated with copper to keep it from rotting is also a factor in restricting roots.  Copper retards root growth.  I recommend removing the burlap.

Planting Trees Correctly to Ensure Their Success

Planting Trees Correctly to Ensure Their Success

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

Planting a tree isn’t as simple as digging a hole and sticking it in.  Many trees fail to grow and thrive because they aren’t planted correctly.  To determine just what is the “right” way to plant a tree, let’s look at some of the most common mistakes made when planting a tree or a shrub.

Too Deep

Probably one of the most common reasons for failure in planting trees and shrubs is that the root system is planted too deeply.  Roots need air.  They should always be planted at the same level or slightly above the level that they were growing in the nursery or in their container.  Planting them deeper than this deprives the roots of air and will eventually kill most plants.  Death is not usually a sudden thing.  Trees planted too deep will fail to grow well.  Leaves and new growth will be undersized.  Leaves may develop leaf scorch along the edges or become yellow and drop off the tree.  Keep in mind that trees aren’t tomatoes, most won’t tolerate deep planting.

Planting With Material Around the Root Systems

Any material around the roots... plastic twine, burlap, boxes, paper pots, and plastic pots should be removed at planting time.  Most gardeners don’t have to be told to do this, but you’d be surprised at how many people belatedly find trees and shrubs planted with the roots still in a plastic pot.

Whether it’s a non-degradable material like plastic or a material such as paper which will eventually rot, it should be removed.  Materials like cardboard boxes and pressed paper pots do rot, but they don’t rot quickly enough in our garden soils.  They impede water movement and restrict root growth.

The same holds true for burlap.  Even though burlap seems to rot readily it doesn’t rot as quickly as we would anticipate.  Some burlap is even treated with a copper material to retard decay.  Since copper is toxic to root tissues, the roots won’t grow through the burlap layer even if the burlap has decayed.  In some instances, plastic burlap is used.  That definitely won’t decay any time in the near future.

Dense Root Masses and Encircling Roots

When left growing in containers too long, many trees and shrubs develop cramped root systems, which make it difficult to grow them with success.  For plants to survive and grow, you will need to loosen the roots of those with dense, fibrous root systems.  When roots are dense and matted, cut them with a shovel, spade, or knife.  Make six to eight shallow vertical cuts into the exterior root mass.  Use your fingers or a hand fork to loosen the cut roots and help spread them out.

Another method of remedying problems with dense root masses of container grown plants is to “butterfly” the bottom of the root mass.  Use a shovel or spade to divide the bottom half of the root mass, creating two flaps or “wings.” The “wings” are kept apart by with soil, a stone, or a stick before filling the planting hole with soil.  Make six to eight vertical cuts to the exterior roots in the uncut, top portion of the root mass.

Plants with thicker, woodier roots, often develop encircling roots when grown in a pot too long.  These roots will keep growing in circles, if they aren’t disturbed at planting time.  The roots should be cut and spread as just described above.  With encircling roots the plant eventually chokes itself to death. Circling roots can’t reach out in the soil for water and nutrients needed for healthy growth and the poorly established root system doesn’t perform its anchoring function very well.

Clay Root Balls

Many quality nursery plants sold in this area are dug from nursery fields in the Williamette Valley in Oregon.  Many of these fine plants have one major drawback... the soil in the root ball is a heavy clay.  This clay is very different from local yard and garden soils.  It’s dense and holds onto water very tightly.  When the landscape is watered to accommodate our lighter, more droughty soils, the plant ends up with roots that are constantly too wet because of the clay soil around the roots -- this often leads to root rots.

One can avoid the problem by avoiding the purchase of plants with clay soil or one can try to remedy the situation by gently forking soil away from the root system and exposing the roots.

Creating a Bathtub Effect

Adding organic matter such as peat moss, compost, or mulch to the backfill soil of a planting hole is not a good.  It generally is not helpful and can create a “bathtub” effect.  Water easily enters the coarser soil in the planting hole but drains our slowly because the surrounding soil is more dense.  Again, the roots stay wet for long periods of time and root rots are very likely to develop.

However, when planting an entire landscape bed or border amending the soil with organic matter is a good idea.  Loosening the soil and adding the organic matter fosters good root growth.  Preparing the soil in the entire bed for planting eliminates the bathtub effect that can occur with planting holes.

Compact Soils

In planting sites around new homes and buildings, the soil is often very compacted.  This is especially true on commercial sites where the soil had been compacted with heavy machinery to provide a suitable area for paved parking.  Roots of trees, shrubs, and other plants have a hard time growing in compacted soil.  Water doesn’t move well into and through compacted soil.   There isn’t as much oxygen available to plant roots in a compacted soil.  Because the soil is tight, roots have a hard time penetrating the soil.

The best thing that can be done in a new planting area to relieve soil compaction is to loosen the soil by physically disturbing the soil by deep tilling or digging.

Proper Planting Techniques

  1. Dig the hole deep enough to accommodate the root ball.  Keep in mind that the top of the root ball should be level with the soil or slightly above it.  The planting hole should be at least twice the diameter of the root ball.  The wider the hole, the better. Note: Always lift your tree and shrub by the root ball, not by holding onto the trunk. 
  2. For balled and burlapped plants, first situate the plant in the hole and then remove all twine, string, or wire from around the root ball and stem.  Cut the burlap away from the root ball, removing as much as possible from the hole. For container-grown plants, cut and loosen roots if needed before placing the root ball in the hole.
  3. Add appropriate amounts of slow-release nitrogen fertilizer to the planting hole. Backfill with the native soil you removed from the hole. Do not amend the backfill soil with organic matter. Gently firm the soil around the roots and definitely don’t tamp the soil down around the roots with your feet.
  4. Water the plant thoroughly to help settle the soil around the roots.  Mulch the entire root zone area with bark mulch.
  5. Keep the soil around the roots moist but not wet and saturated.
  6. Prune to remove only the broken branches.