String Trimmers and Trees – Not a Good Idea


As spring rains have caused rapid growth of lawns and the need for frequent mowings, I have once again seen fresh examples of severe damage to landscape trees.  Careless use of string trimmers is the most common cause of severe damage to trees that I see during the many site visits I make to help people evaluate their landscapes and diagnose tree problems.  When the bark gets damaged, sap flow is reduced to leaves and tree quality declines.  More damage with each use of the trimmer can eventually result in the death of the tree.

The cure is very simple:   String trimmers should never ever touch the bark of a tree, no matter the age or size of the tree.  I repeat:  NEVER, EVER.  The damage inflicted from one careless round of string trimmer use can run into hundreds of dollars if the bark is touched by the trimmer string.

Very often the damage is gradual, but cumulative.  There’s no more reason to hit the living bark of a tree, than there would be to weed whip your bare leg.  Both are living tissue and both say “ouch” if you hit them with a string trimmer.

The following are ways that grass/weeds around trees can be safely controlled:

1) Trimming with hand operated grass clippers

2) Kill grass and weeds around the tree with roundup herbicide (avoid contact with the bark) and use a bark/wood chip mulch to keep a 3’—4’ circle around the tree free of weeds/grass

3) Heavy-duty tree guards that deflect the string of a power trimmer.  Thin plastic won’t be good enough.

4) Plastic or rubber mats around the tree (must have the hole for the trunk enlarged on an annual basis to accommodate the growth in trunk diameter.

5) Give the person/company that carelessly damages tree bark a $50 bill for each tree, for each time, they touch the tree bark, and insist they pay the bill, or pay to replace the damaged tree!  I suspect they will stop hitting the bark.

CAUTION:  This information will ruffle some feathers.  Be prepared for push back, but be firm and insist that trimmers never ever touch tree bark, no matter how large the tree.  (I even see severe damage to wooden fence posts from string trimmers!)