There are several reasons why you should keep the grass back from the trunks of your trees. 




String-trimmer damage to tree trunks is not reversible. Period. The vascular system that is damaged does not repair itself or re-grow after it has been damaged. Trees may show varying amounts of stress from string-trimmer damage, and the wound is a perfect place for disease organisms to enter the tree.







If grass has grown into the mulch ring around your tree, DO NOT USE HERBICIDE TO KILL IT! Herbicide drift to the trunk is common, and the damage is not reversible. Use a HOE or pull the weeds/grass with your hands. There is no safe herbicide to use under the canopy of a tree, especially close to the trunk. Drift is almost certain, and volatilization of the herbicide can cause the lower limbs to die. The lower branches of this Mexican White Oak have been damaged due to herbicide drift and volatilization.





Fruit trees suffer when they must compete with lawns for water and nutrients. Keep the area under the canopy free of  grass and weeds, and apply a 2″ layer of mulch under the canopy. Do not allow the mulch to touch the trunk of the tree, but pull it back six inches from the trunk. You can see string trimmer damage at the base of this peach tree’s trunk where disease has entered.