A stringline trimmer aka ‘weed whacker’ can be a tree’s greatest enemy.
Just inside that ‘dead looking’ outer bark of a tree trunk is living tissue in need of your protection. Damaging that living tissue can lead to the death of the tree, by opening a pathway to insects and disease.
Since Dogwood trees have a thin layer of outer bark, and are often killed by a bark borer, they are considered one of the most vulnerable trees to stringline trimmer damage. Getting bumped with a lawnmower can be just as bad.
One of the most common ways to protect trees from ‘weedwhacker death’ or getting ‘skinned’ by lawnmowers, is to create and maintain a protective mulch circle around the base of a tree.
That being said, mulch should not be piled-up against a tree trunk, creating what’s often called a ‘mulch volcano.’ If you use an herbicide to control weeds in that mulch circle, be sure to use one that won’t leach into the soil and get absorbed by tree roots.
An important added benefit of maintaining a mulch circle around a tree, is that it eliminates competition from lawn grasses. That’s right, grass can compete with a young, newly planted tree, for water and nutrients.
Needless to say, try not to damage tree roots or the tree trunk, when creating a new mulch circle. And don’t pile mulch against a tree trunk, give it some breathing room.
Finally, here’s a video on using a gas powered weed whacker. NOTE: Since recording this video, I changed the weed whacker head to one where you insert three pieces of pre-cut trimmer line, which creates 6 lines for better cutting power. As a second option, you can also convert it to 3 plastic blades for heavier weeds. It cost about $25, and I see there are several ‘universal’ ones like it, available at big box stores now. It’s definitely far less hassle than the one seen in this video!