How you prune a plum tree depends upon the tree's age. Young trees, up to age 4, are pruned more heavily than mature plum trees. It is important that your pruning implements are sharp so that you can make clean cuts and avoid crushing the wood. Plum trees are susceptible to silver leaf disease, caused by a fungus that is productive in winter when the weather is damp. Pruning the tree at this time is not advised. Instead, prune a plum tree from mid-June until August.
Remove any suckers growing at the base of the prune tree. Suckers are small plum tree sprouts that either grow from the trunk or from the soil surrounding the tree. Use the pruning shears to cut the sucker to ground level.
Cut out any dead branches and those crossing over others.
Prune off new growth on the sides of the plum tree. From the tip of the branch, cut back to where you will leave six leaves.
Cut the main branch of the plum tree if it is 8 feet high or taller. From the top of the tree, cut it back to 3 feet above the first set of branches you come to.
Remove and dispose of all pruning debris and water the tree until the water puddles.