Trees: Damage
Changes in soil grade
Even a few inches of fill or soil removal can cause extensive root damage. If possible, never remove soil from or add large amounts of soil within the drip line. When soil air is decreased by filling, certain gases and chemicals increase and become toxic to roots. Symptoms may appear within months or years after filling has occurred.
The extent of injury from filling varies with the species, age, and condition of the tree; the depth and type of fill; and drainage. Beech, dogwood, most oaks, pine, sugar maple, spruce, tulip popular, and walnut are the most easily injured. Elm, locust, pin oak, sycamore, and willow are the least effected. Clay soils cause the most damage because the fineness of the soil shuts out air and water more than a gravelly or coarse soil. Three to four inches of soil can be added to small areas under the tree provided the soil texture is coarser than the native soil. Finer textured soils should not be used for filling.
If a tree well is to be constructed, built a wall no closer than the dripline and grade the soil outside of the tree well so it drains away from the tree. Success has been reported in some cases where gravel was spread over the existing grade and vertical pipes were installed every 10 feet before the area was covered with a coarse-textured fill soil. Building a tree well several feet from the trunk of a tree before adding several feet of soil will do little to prevent root death.
Damage from filling
The base of a tree at the soil line should flare out (be wider than the tree trunk a foot above the soil line). If the tree does not have a flare, but enters the ground in a straight line, fill dirt has been added. Digging will reveal the depth of the fill. Other visible symptoms include small leaves, many dead twigs, and the presence of numerous suckers along the main trunk and branches. If the filling was recently done and roots have not begun to regrow into the fill, efforts should be made to restore the soil to its original level.
Damage to roots
Damage to trees during construction usually involves impairment of the water and nutrient supply system. Therefore, three corrective procedures should be applied: thinning branches to reduce water requirements; irrigating as needed to maintain an adequate moisture supply, and applying fertilizer to help stimulate new root growth (avoid excessive nitrogen). Limited or no tilling should be done under damaged tree until they have had adequate time to recover.
A moderate application of fertilizer may be beneficial. Use 2 pounds of 5-10-5 per inch of trunk diameter measured three feet above the ground. Excessive applications of nitrogen will promote new foliage growth that the tree can not support with its reduced root system. The easiest and most practical method of application is to broadcast the fertilizer over the area of greatest concentration of feeder roots. These are located in a band around the tree starting about two feet from the trunk and extending several feet beyond the ends of the branches. Scatter fertilizer evenly over this area, and apply water liberally to wash it into the ground.
Keep the tree mulched and well watered during stress periods. Gradually prune and reshape the tree for balance and general appearance over a period of 3 to 5 years. Control devitalizing conditions such as sucker sprouts, insects, and diseases.
Storm Damage
Treatment of storm-damaged trees requires wise decisions and prompt action if the maximum benefit from repair work is to be achieved. Repairs come in two stages: first aid for immediate attention; and follow-up work to be distributed over a period of months to several years. Care for damaged large trees is best left to professionals.
First decide if the tree is worth saving. Does the tree serve a needed function or does it have sentimental or historical value? If over 30 to 50 percent of the main branches or trunk are severely split, broken, or mutilated, the benefit of extensive repairs is questionable. You probably would not want to save less desirable trees, such as black locust, Siberian elm, box elder, mulberry, poplars, and silver maple. More desirable trees, such as oak, maple, pecan, pine, magnolia, holly, and beech may be worth saving unless severely damaged. If the trees are close to power lines, building or other structures, the tree should be removed by a professional. Extremely old, low-vigor trees might not have the ability to recovery.
Small trees which are uprooted should be straightened and staked immediately. Left exposed to sun and wind will severely damage any upturned roots. Remove any damaged roots or branches. Some staking or cabling may be necessary.
Cut off broken and split branches but delay pruning to reshape the tree. Too much removal of wood in one season can create such problems as sunscald, weak branching habits, and sucker growth. Reattach trunk bark to the inner wood with galvanized nails if healing seems possible or trim the wound edges to promote healing. Promptly remove all debris such as broken branches and prunings to help eliminate breeding grounds for insects and diseases.
Lightning
Lightning strikes can cause various symptoms. They usually loosen bark which hangs in strips. The amount of bark loosened depends on the severity of the strike. The lightning bolt may have passed through the trunk and caused considerable internal wood damage that may not be visible. If only a small amount of damage occurred, remove damaged branches and loose bark and provide excellent cultural practices (mulch, water during drought, and fertilize). Damaged trees can die within a short period of time or years later following a period of stress.
Snow/ice damage
Snow and ice on branches can cause them to break or bend from the extra weight. High winds will compound the damage. The result is often misshapened plants from broken or split branches. Little can be done about removing ice from plants. Snow can be removed with a broom. Always sweep upward --- lifting snow off. When the branches are frozen they are quite brittle.
Do not be in a hurry to prune to correct plants bent out of shape by snow or ice. Often the plants will straighten up in a few days by itself. Broken branches, however, should be pruned as soon as possible. Proper pruning is effective in minimizing potential damage from ice and snow. Particularly important is the removal of weak, narrow-angled, v-shaped crotches.
Water Stress
Most plants wilt when they experience inadequate moisture. Leaves on river birch and poplar trees turn yellow and drop. Sycamore leaves turn brown and fall, while other trees develop premature fall color or shed small branches.
A condition known as leaf scorch can develop on plants, such as dogwood, maple, beech, ash, and elm when their root systems can not replenish moisture as fast as it is lost from their foliage. This disorder can be caused by a limited or damaged root system, drought, and hot, windy conditions. The leaf tissue on the edges and between the main veins dies and turns brown. Eventually the entire leaf except for a narrow band along the veins die. Plants can be affected uniformly or only on one side. Plants growing near reflective surfaces such as roads and patios, as well as, recent transplants are more likely to be affected.
A similar condition can develop during the winter from desiccation. It is particularly important to provide relatively high soil moisture for evergreen plants prior to a severe freeze.
Damage to Tree Trunks
Bruised and peeled bark
Bruised and peeled bark should be treated to promote rapid healing. Trim around the wound to sound tissue on each side (Figure 1). Use a sharp knife and do cut any deeper than necessary. The top and bottom should be rounded instead of forming a sharp point. This will facilitate movement of moisture and nutrients around the damage area. When done properly, healing will occur completely around the wound.
If the damaged area is less than 25 percent of the circumference of the trunk, the wound should gradually heal over and no permanent injury should result. If the damage involves more than 50 percent of the circumference, the tree may be seriously reduced in vigor. It may lose branches and become quite unsightly. However, the corrective procedures of pruning, irrigation, and fertilization should be practiced until the tree recovers or until it is evident that the tree should be removed.
Lawn mower and weed-trimmer damage
Injury and infection started by a lawn mower or weed trimmer can seriously threaten a tree's health. The most severe injury occurs when the tree bark is slipping (loose due to cambium growth), in early spring during leaf emergence, and in early fall during leaf drop. The site of injury is usually the root buttress, since it flares out from the trunk and gets in the path of the mower or weed-trimmer. Although large wounds are more serious, repeated small wounds can also add up to trouble. Injury can be prevented by the removal (by hand trimming) or prevention (use of a herbicide or mulch) of grass and weeds from growing at the base of the tree.
Wounds are serious enough by themselves, but the wounded tree must also protect itself from pathogens that invade the wound. These microorganisms often attack the injured bark and invade adjacent healthy tissue, greatly enlarging the affected area. Trees can be completely girdled from microbial attack following injury. Decay fungi also become active on the wound surface, and structural deterioration of the woody tissues beneath the wound will often occur.
