Lawn Maintenance: Beware Bump Damage to Trees

During one or more of these mowings a bump of tree trunks is not uncommon as we try to mow close to the trees to avoid trimming or at least keep trimming to a minimum. Few of us realize the possible consequences that may develop from such damage to the trunk of a tree. Of course, not all bumps are bad bumps causing irreparable and fatal damage to the tree. Still, the wound from a single bump may eventually lead to death although it is more likely that a tree damaged in this way has been subjected to frequent bumps in the same location.

Young trees are more likely to be damaged by lawnmower bumps. The tree that is only a few years old has rather thin bark. At this stage, even a slight bump might mash the bark resulting in an open wound. Older trees, especially those which develop a thick, corky bark, are better protected and may never develop this problem. One might ask why a lawnmower bump should cause concern because trees normally recover well from pruning cuts, from slashes with knives, or even from natural damage such as sunscald. Part of the answer to this is that these types of damage normally occur higher on the tree.

A lawn mower bump is close to the soil where the bark tends to stay damp. It is also a type of wound that is not clean and tends to heal slowly. This slow healing, along with long periods of moist conditions make an excellent place for the establishment of disease organisms. If the damaged tree is susceptible to any of the fungus diseases that work in the vascular systems beneath the bark and form canker diseases, the lawnmower bump has given it a place for one to get started.

Even some organisms that normally are not a problem, get entrance in this way, and work slowly beneath the bark until some time later the disease becomes extensive enough so the tree declines. At this stage growth slows, leaves become smaller, flower and seed production increase until the tree may finally die. This does not mean that those that may have bumped trees are destined to have a treeless prairie around their homes in the future.

It is important, however, especially in the care of young trees to keep grass away from the base of them. This bare strip of soil around the tree should be wide enough so there is no danger of hitting the base during normal lawn maintenance. Also, the lack of grass close to the trunk, keeps down humidity so a wound is less likely to become infected. If damage is evident to the base of a tree, use a sharp knife to clean away loose bark. Carve the wound smooth and clean so that rapid healing can take place.

Above all, avoid bumping a wound a second, third, or fourth time. Lawnmowers are not the only home garden implement that can cause damage. In winter, snowplows can also cause the same damage. Be careful in the use of trimmers with rapidly rotating nylon line. These too can easily whip off the bark of young trees, leaving an open wound subject to future problems. Lawn and garden equipment is extremely helpful, but must be used with care.

Mac Perry's Florida Lawn and Garden Care, by Mac Perry.