Prune Santa Rosa plum trees during the dormant winter months or early spring. Pruning the tree controls the height for easier harvesting, eliminates branches that are ill-placed, and opens up the tree to light. Summer pruning causes a dwarfing effect and is practiced if a smaller tree is desired. Santa Rosa grow in a spreading manner and should be trained to an open center shape.
Prune Santa Rosa plum trees immediately after planting. Remove lower branches to allow mowing underneath. Allow about 12 inches of growth above this with three to five bud shoots. The pruned tree should be about 2 1/2 to 3 feet in height.
Prune lightly during the first 5 years. Prune young trees lightly to develop the desired shape. Remove excess limbs, leaving three to five lateral branches to form the main scaffold limbs. Trim back branches that grow toward the center.
Allow secondary branches to develop during the second and third years.
Prune mature trees heavily, especially when revitalization is necessary. Bearing trees need increased pruning to stimulate growth of terminal branches and fruiting spurs. Prune mature trees heavily at the top. Top the tree to limit the height and allow easier harvesting.
Prune to reduce tree size and stimulate growth. Remove large branches by cutting underneath the branch, then finishing the cut flush with the main branch or trunk. Avoid leaving stubs or damaged bark.
Apply wound dressing to large cut areas. Use a wound sealing compound to dress large wounds and speed healing.
Prune away excess fruit while the fruit is young, about a month after the trees bloom. Hand-pick the excess fruit, leaving fruit about 3 to 5 inches apart. Removing excess fruit protects the limbs from breakage and encourages the plums to grow larger.
Prune again in June, after the plums have been harvested. Cut back the long whips to 1 to 3 feet to limit the next year's fruit load and protect the tree.