Lawn Mower Damage
Have you beaten your tree lately? Maybe you
ran into it somewhere. If you did accidentally, you are destroying
the vitality of your tree more than you know. Most people
do not understand that injury and infection started by lawnmower
wounds can often be the most serious threat to tree health.
Lawnmowers cause the most severe injury during
periods when tree bark is most likely to "slip"
which is in early spring during leaf emergence and in early
fall during leaf drop. If the bark slips, a large wound is
produced from even minor injuries.
Most tree injuries occur when mower operators
attempt to closely trim grass around trunks with a push or
riding mower. You can prevent this scenario by removing the
turf around the tree, or by hand trimming.
The site of injury is usually the root buttress,
since it flares out from the trunk and gets in the path of
the mower. However, injury is also common anywhere from the
roots up to several feet above the ground.
Although large wounds are most serious, repeated
small wounds can also add up to trouble.
Wounds from lawnmowers are serious enough by
themselves, but the wounded tree must also protect itself
from pathogens that invade the wound. These micro-organisms
can often attack the injured bark and invade the adjacent
healthy tissues, greatly enlarging the affected area. Sometimes,
trees can be completely girdled from microbial attack following
Decay fungi also become active on the wound
surface and structural deterioration of the woody tissues
beneath the wound will often occur. Many wounded trees that
are not girdled may eventually break off at the stem or root
collar due to internal decay.
Bark can often be successfully reattached to
trees if the wounds are treated within a few hours after injury
occurs. Torn bark should be reattached as close as possible
to its exact pre-injury position and held in place by a few
small tacks or staples.
If several days or weeks have passed since
the injury, torn or loose bark should be cut away and the
edges of the wound should be traced using a hand tool such
as a pruning knife.
Pruning tools should be sterilized with a weak
bleach solution before working each tree. There is no need
to cut additional tissue around the wound to achieve a certain
shape. Avoid making deep scribes or any vertical sharp points
that would serve as additional sites for bark die-back or
starting points for bark cracks.
Older injuries with callus development all
around the wound are best left alone. If there is any dead
bark old wounds, it is advisable to trace the area back to
live bark. Application of wound dressing for cosmetic purposes
Spreading organic materials such as leaves,
grass clippings or straw under and around trees will effectively
control grass and weeds and provide an attractive appearance
around the base of the tree.
Not only will mulching with organic materials
prevent grass competition, it will also conserve moisture
for use by the tree roots and stabilize soil temperatures
(since roots don't like extremely hot or cold soils). Young
trees should be surrounded with at least 3 feet of a thick
mulch (3 to 4 inches deep) that is maintained throughout the
If trees are closely surrounded by tenacious
grasses such as bermuda, the turf should be removed or killed.
The safest grass killer that can be used near young trees
is glyphosate which is sold as Roundup, Kleenup, Weed Away,
and Weed and Grass Killer. This herbicide will totally eliminate
grasses, roots and all, yet is inactivated upon soil contact.
Be sure to use a piece of wood, cardboard, etc., as a shield
during spraying to prevent spray droplets from touching the
trunks or foliage of your desirable plants.
Grass and/or weeds should be removed from around
tree trunks and beneath trees if maximum growth is expected.
Grass and/or weeds compete for the same nutrients and water
that the tree needs. During the summer when rainfall is low
and less than adequate watering occurs, the competition for
water imposed by weeds or grass turf can substantially reduce
tree growth. When competition from grass is eliminated, tree
roots are more evenly distributed, root numbers are higher
and they utilize a larger volume of soil. Effective utilization
of soil by a larger root system will mean that the fertilizer
you have added will be utilized more fully.
Liberal watering can offset the retarding effect
of grass. Obviously, if the competition with grass for water,
which the tree needs during dry periods, can be overcome by
extra watering, the tree will have a more optimum growing
condition. Your trees need a deep, thorough soaking once a
week in the growing season either from natural rainfall or
from supplemental irrigation. Whenever you must irrigate,
be thorough and allow the water to deeply penetrate. The best
way to water large trees is to let water slowly flow onto
an area under the drip-line of the trees for several hours.
Remember that watering which is adequate for lawn grasses
growing under trees, IS NOT adequate enough to provide for
the needs of an actively growing fruit tree!
The problem of lawnmower injury is not a tree
problem but a people problem. It is a classic case of communication
breakdown. The solution is to educate lawnmower operators
about how serious these wounds can become and also to protect
trees from careless grass trimmers such as weed-eater maniacs
and lawnmower jockeys who enjoy using tree trunks as crash
sites. A mulched area around the tree trunk can provide protection
from these types of tree-damaging behavior.
So if you want fast growing trees don't abuse
them with weed-eaters and lawnmowers! Spread some organic
material around their base and keep weeds and grass at bay.