Pruning low grow sumac
In late winter, remove all dead, diseased or damaged branches. Disinfect the clippers following each cut if there are oozing cankers or evidence of viral disease on the diseased branches. They can be dipped in or wiped with rubbing alcohol or a solution of 1 part chlorine bleach to 9 parts water. Next cut back the branches that are at or near the bounds of the growing area for the sumac. Cut the branch just beyond a bud that is growing in the direction you want the branch to grow or at a lateral branch that is a least one-third the diameter of the branch being cut. Finally, remove up to one-fifth of the older branches near the ground.
After several years' growth, the "Gro-Low" sumac may become tangled, overgrown and oversized, particularly if there has been little regular maintenance. When this happens, all of the branches can be cut back close to the ground. By summer an excessive number of vigorous new shoots may have appeared. Remove some of these shoots to prevent the plant from becoming too dense. Cut others back to a side bud to prevent the shrub from outgrowing its space too quickly.