This picture is an example of how newly planted Shade Tree Commission trees are being destroyed by weed wackers.  We assume this location was a landscaping company and hope this acts as a reminder that damage to tree bark is the most common cause for losing trees.
When a tree is injured, the injury generally breaks the bark, reducing the tree’s ability to absorb water and nutrients.  The wound exposes the inside of the tree to pests and diseases, which include bacteria and fungi that can cause discoloration and decay of wood.  Once decay enters a tree wound, the tree cannot be cured; decay weakens stems and shortens the tree’s life.
Damaging tree bark with a string trimmer is easy to do.  You think you’re being careful, but you get distracted.  The string strays off course for just a second and cuts through the tree’s protective bark.  The damage a string trimmer can do ranges from cosmetic damage to killing the tree.  Proper trimmer use and preventive care will keep your trees healthy and free from damage.
Healthy, mature trees usually recover from slight damage.  The remaining bark and cambium layer are adequate to carry sap and nutrients up and down the tree.  The tree can wall off a few inches of exposed wood with a callus to protect it from pathogens.  Small wounds can kill young trees if the tree’s systems are damaged severely.  If damage — no matter how thin — completely circles the bark of any tree, death is almost certain.  In effect, this damage — called girdling — removes the tree’s circulatory system.  Old and sick trees are more vulnerable to disease and insect infestation.
Good Trimmer Use
Keep the string trimmer well away from the trunks of trees and shrubs.  Use as much care near a big tree as you would near a tender annual.  If you hire a landscaper, have a talk about your expectations for careful trimmer use.  Use handheld clippers to knock off the last few inches of grass and weeds near a tree.  You can also pull small, tender grass and weeds by hand.  Keep your string trimmer in good repair so the string doesn’t suddenly slip out and become longer because of worn components.
PLEASE PROTECT OUR TREES!   STREET TREES ARE PAID FOR WITH YOUR TAXES!