Hello Gardeners, I’m Amanda McNulty with Clemson Extension and Making It Grow . Properly planting a tree involves knowing basic steps that end with putting down mulch. Mulch actually protects a tree from competition from turfgrass. Grass has a thick, shallow root system that can out compete the tree’s roots for nutrients and water. But that’s not the only harmful effect when grass grows over the tree’s root zone. Grass needs to be cut, and many trees are wounded when the lawnmower hits the trunk