Common Root Problems

Common Root Problems

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist  

Root problems are the number one cause of tree and shrub death in the home landscape. When the general care of a tree or shrub is adequate, root problems are suspected when a plant is growing poorly or showing signs of dieback.  Other symptoms of root problems include chlorosis (yellowing of the leaves) and leaf scorch (brown tips and edges of the leaf). Here are some of the most common root problems that lead to plant death in our local landscapes.   

PLANTING TOO DEEP:  Tomatoes don't mind a deep planting, but most trees and shrubs suffer from being planted too deep.  Plant roots suffocate and die when planted too deep because the roots can’t get the oxygen they need. Trees and shrubs should be planted at the same level as they were in the nursery or just slightly higher to allow for some settling of the soil.  This means that the top of the root ball should be at or just below the soil surface.

If you have trees or shrubs planted in the last five years that haven't grown very well and have exhibited chlorosis, leaf scorch, or die‑back of the twigs, check to see if the roots are too deep.  It's easy to check.  Just take a garden trowel and start digging down at the base of the trunk.  Just under the top of the soil you should be able to find the main roots radiating out from the trunk.  If you must dig down more than two to three inches to find the main roots, you and your plant have a problem.  While troublesome, replanting at the right level is probably the only real solution.

IMPROPER PLANTING: Improper planting should be suspected if the plant looks OK but doesn't grow much after several years from the time of planting or when the plant begins to decline after several years, often with symptoms of leaf scorch and chlorosis. 

When planting a tree or shrub that’s been grown in a container, encircling roots should be gently spread before planting.  Dense masses of fine fibrous roots need to be cut and teased out of the root mass.  Paper pots and burlap should be torn away or removed from the root ball once the plant is situated at the right level in the hole and positioned correctly.  This is especially important if the burlap is green or has a green tint to it.  This burlap has been treated with a copper solution to keep it from rotting in the nursery.  Copper is toxic to roots, so roots will not grow through this copper "barrier" even after the burlap begins to rot.

You can check for root growth by digging down at the edge of the original root ball.  Look for any root growth that has occurred since planting.  If plant roots weren't loosened or spread, it's likely that roots have not grown out from the original root mass. 

This problem occurs most frequently with plants grown in plastic pots, especially when the plants are simply "popped" out of the pots and plunked into a hole without any loosening of the root ball.  If someone else planted your landscape for you, you may want to check the situation of the roots before problems become apparent.  Replanting is the only recourse in this situation too.

WATERING: Because many container grown plants are grown in a "soilless potting mix" which is a coarse mixture high in peat moss or other organic matter, water does not move easily from the surrounding soil into the root ball.  You may have to water the individual root ball directly and not rely on sprinkler irrigation to provide adequate water.

It's especially important to keep the root ball of recently transplanted trees and shrubs moist for the first several months after planting.  Their roots are confined to a limited space, so they're unable to “reach” for moisture further outward or downward in the soil.  With our typical local summer climate, it's essential to pay close attention to watering the first summer after planting.  However, it's also important not to drown plants with too much water.  Don't allow water to puddle around the trunk or keep the roots saturated for any length of time. 

How can you tell if the soil is moist, too dry, or too wet?  Use a trowel, shovel, or soil tube to check for moisture in the root ball.  A dry soil will crumble when you try to make a ball of it in your hands; a moist soil will form a ball; and a wet soil will be muddy with excess water that can be squeezed out.

ROOT DAMAGE: Root damage can occur from any number of situations.  The most common cause of physical damage is from construction, such as trenching for utilities, driveway installation, or digging of septic systems.  Roots are often cut to accommodate the construction without the consideration of the damage caused to the tree.  Cutting off major roots, severs the main "pipelines" for the tree.  The tree can no longer access water and nutrients through the severed roots.

Root damage can also occur from a change of grade.  Most of the water and nutrient absorbing fine roots are in the top one-foot of soil.  Changes of grade in excess of four inches can severely reduce the amount of oxygen and water reaching these roots, eventually killing them.  In some cases, soil compaction and not extra soil from a change in grade can lead to the decline and eventual death of a tree.  Soil compaction also restricts oxygen and water uptake by the roots, leading to root decline and death.  Severe soil compaction is associated with roads, driveways, and the use of heavy machinery.  Moderate compaction can develop over time simply from human and animal foot traffic or from impact sprinkler irrigation.  This type of compaction can be partially alleviated with the use of a mechanical aerator.