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By Noel Mues Extension Educator Green-up time in the spring focuses attention on potential insect and disease problems of trees. However, we as homeowners and yard tenders may be guilty of causing some of the worst and needless damage to trees – lawn mower damage or “ mower blight”. Symptoms of mower blight are wounds of varying size on a tree trunk at about mower height and lack of normal root flare at the base of a tree. This can lead to overall tree decline, including crown dieback, stem rot and leaf drop. Many people think that a tree’s bark protects it from small bumps and scrapes. This is true to a point, but a tree’s living, growing tissue, the cambium layer, is right underneath the bark and is easily damaged. Weed whips also can severely damage tree trunks. The nylon cord of even the smallest of these tools can quickly kill succulent tissue below the bark. The best approach to preventing mower and weed whip blight is to mulch the tree. A four inch depth of organic mulch, such as wood chips, bark or pine needles should be used rather than rocks or plastic. Distribute the mulch for several feet around the tree. The larger the mulch area, the better. Mulch will keep grass from growing next to the tree. Grass competes with the tree for water and nutrients. It will also keep the lawn mower away from the tree trunk. Other benefits from mulch include: it keeps the soil around the tree roots cool and moist, reduces compaction, and adds organic matter and nutrients to the soil as the mulch decays. Mulching also reduces conflict between tree roots and mowers. These are good reasons to mulch around a tree even if you are careful with the mower. Many tree species, such as silver maple, have roots that emerge from the soil over time and become a nuisance. If these roots are cut and removed to allow easier mowing, the tree will be stressed. Mulching will eliminate the need for removing these roots unless they extend a considerable distance from the tree. Non-permeable plastic sheeting should never be used as mulch under trees or shrubs and should not be placed under a bed of chips or rocks. Roots need oxygen that enters the soil from the air above. Plastic sheeting prevents oxygen from entering the soil, causing root suffocation and eventual decline of the tree. |
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