Homeowners often want a tree that grows fast, isn’t messy, provides abundant shade, and is free of insect and disease problems. However, once planted their tree of choice begins to decline in just a few years. Three main types of damage to root systems occur in young trees.Download a Printable PDF
Circling roots cause by a container
Homeowners often want a tree that grows fast, isn’t messy, provides abundant shade, and is free of insect and disease problems. However, once planted their tree of choice begins to decline in just a few years. Three main types of damage to root systems occur in young trees.
CIRCLING ROOTS AND CONTAINERS
When roots are left in a container too long, they often follow the shape of the container and grow in a circle, failing to expand outward. In some instances the roots stay like this, resulting in a root system that cannot supply enough water and nutrients to the tree. Additionally, a circling root can grow around the base of the tree, girdling it and interfering with absorption. Initially, the tree appears healthy, but after several years it may decline in vigor and die.
Roots can be crushed, broken, or left behind during the lifting process in the field nursery or during transplanting. This most commonly happens to large caliper (1-3” diameter) balled and burlapped trees that have been mechanically lifted, wrapped, and transported.
During cultivation, extra soil is often piled around the trunk of the young tree. If this extra soil is not removed before lifting, part of the lower root ball may be lost.
IMPROPER PLANTING TECHNIQUES
Too often trees are planted into too small of a planting site, too deep in the soil, or into soil without the proper nutrients.
A planting site that is too small can crowd roots so they cannot grow outward. A planting site should be at least 2-3 times wider than the diameter of the root ball since the majority of a tree’s roots grow laterally away from the tree.
Trees are often planted too deep because of the way they appear in the container. In nursery containers, the primary root system is found at the bottom of the container where they can absorb nutrients, water, and air through holes at the base of the container. So when planted, it is natural to assume that the roots are in their proper placement and the tree is planted at the proper depth, the top of the container. However, it is important to find the top most root, which may be several inches down, even into the lower 1/3 of the container, remove the excess soil on top. Then when planted, the main lateral root should be at the ground surface, rather than several inches below—as they often are within the container or burlap.
Another concern of improper planting is the soil. During construction, topsoil is commonly removed or covered with subsoil and construction debris, leaving planting sites that are low in organic matter, high in clay content, high in pH levels, and usually compacted. Roots cannot readily penetrate these poor quality soils and the tree slowly declines over a few years.
Environmental conditions in Nebraska make it difficult for many trees to survive or grow well. Various soil types, heat, fluctuating winter temperatures, desiccating winds and drought all contribute to stressful conditions for trees. The following list is a guide for selecting trees to plant along streets, in parks, at schools and other public areas as well as private yards. For specific recommendations on the tree species listed below, visit with your local nursery professional.
|Small Trees (under 20' tall)||Medium Trees (20-40' tall)|
|Large Trees (over 40' tall)||Conifers or Evergreens|
Tree care basics
Follow these basic bare instructions to ensure a healthy life for your new tree:
Choloris or Yellowing
A common problem in Nebraska soils is high pH levels, which cause nutrients to be unavailable to tree roots. The lack of minerals, particularly iron, causes a condition called chlorosis. This abiotic disease is characterized by yellow leaves, slow growth, branch dieback, and sometimes tree death. Symptoms are more severe among trees and shrubs planted too deep or planted in poorly drained, compacted soils or soils with high calcium content and pH levels above 7.5. Applications of sulfur alone or iron with sulfur can help lower the ph. If the tree was planted too deep, the soil can be lowered and removed to the main lateral root or, raise or lift the tree and root system with a tree spade.
Understanding tree growth
Tree roots are believed to grow downward, when actually a tree’s roots can grow outward from the trunk a minimum of 1-2 times the height of the tree. Tree roots need oxygen to live and take up the majority of their water and nutrient needs within 18-24 inches of the soil surface. This is critical for the survival and growth of the tree. Any mechanical work or chemical application that comes in contact within this root zone affects the tree, even 40-50 feet away can result in damage to the roots. A major problem for trees in urban environments is the use of herbicides—dicamba, 2,4-D, and soil sterilants—along sidewalks, driveways, alleys and under fences.
Proper mulching provides benefits
One of the best practices to encourage root development and improve the health of the tree is to mulch around the base of the tree, but DO NOT pile mulch on the stem or trunk where it can cause moisture buildup leading to rot. Research shows that tree root density is significantly greater under wood chips. On the other hand, grasses, especially brome and other sod-forming grasses, can limit root growth. A 6-foot diameter of mulch should be placed around young trees and can be increased to the dripline as the tree grows. For mature trees, an 8-12 foot circle would be beneficial.
Proper watering is critical
Setting specific guidelines for watering is difficult because of variable environmental and soil conditions. The goal is to keep the root ball moist, but not saturated. When planting a tree, check the soil moisture of the root ball and surrounding soil for the first few days. When dry within the top one to two inches, water. This might be every day or every other day for the first several days. After two to three weeks, gradually reduce watering to every three days, then to once per week. Watering should be increased, however, during periods of extremely hot, dry or windy weather. In many landscapes, watering needs to be appropriate for both lawns and trees. Generally, watering lawns runs for shorter durations, watering more often, and shallower than trees. Extending the watering time while reducing the frequency is a good balance. The optimal solution for trees in a lawn is to water twice a week in the spring and fall and three times a week during the hotter months of the summer, July and August.
Selecting and planting the right tree
- Select the proper tree species
The local tree board, county extension, or arborist can recommend the best trees for your area. Fast-growing trees are not the most desirable. Homeowners should select species that will grow moderately, do not spread aggressively, and do not have a history of insect and disease problems.
- Select a quality tree
Healthy trees in a home landscape add considerable value to the property. Extra care/thought should be considered whenever selecting a tree. Nurseries and garden centers that specialize in trees are more likely to offer better plant material than those sold at discount centers, box stores, or other non-garden centers. When looking at individual trees, look at the overall shape of the tree, get acquainted with the nursery and ask for help to inspect the root system. Look for indications that the tree does not have a central leader, the tree is root-bound, the soil around the roots is loose, or that the root ball is broken.
- Plant the tree properly
- Current techniques are important for a successful planting:
- Dig a planting site 2-3 times wider than the root ball.
- Place the tree so the top main root is at the ground’s surface.
- Mulch an area at least 6’ in diameter around the tree with wood chips.
- Do not use plastic or woven barrier under the mulch.
- Do not fertilize the tree at planting.
The key to having a healthy tree in your landscape is to keep the tree growing as strongly as possible. Proper species selection, planting, and maintenance can reduce stress on a tree and increase its natural resistance to insect and disease problems. Careful attention to the root system’s environment is critical for keeping trees healthy.