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Why Santa Rosa Plum Trees Need Pruning and How to Do it Right

How to Prune a Santa Rosa Plum Tree
The Santa Rosa plum tree requires major pruning during the first few years of its growth. But, it's easier than it sounds. Gardenerdy tells you how to prune a Santa Rosa plum tree, to obtain a good yield and avoid problems.
Akshay Chavan
Last Updated: Feb 27, 2018
Did You Know?
Despite its Spanish name, the Santa Rosa plum tree is of Asian origin.
Plums tree
Plums are commonly available in two varieties, European and Japanese plums. European plum trees require much lesser pruning when compared to the Japanese one which have an aggressive growth rate. Japanese plums trees come in a variety of species, such as Satsuma, Santa Rosa, Burbank, Mariposa, and Red Ace. These plums are much softer, juicier, and larger than their European counterparts, though the European plum trees can survive much colder conditions. Most Japanese plums have yellow flesh, with the exception of 'blood' plums which have red flesh.

Santa Rosa plums have a reddish-violet skin which is tart flavored, and yellow flesh inside which is sweet and juicy. This plum tree commonly grows to a height of about 20 to 25 feet. It thrives in the USDA hardiness zones of 5 to 9, and prefers well-drained soils and good sunlight. The only long-term requirement of this plant is careful pruning, especially in the first couple of years. It should be intentionally done in such a way so as to create an open-center or a vase-like adult tree. Pruning helps increase the vigor of the plant, makes it easier to harvest, keeps diseases at bay, improves the appearance, and prevents it from uncontrolled growth. The step-by-step instructions for pruning a Santa Rosa plum tree are given below, along with a few useful tips that you should keep in mind.
Immediately after planting, cut the main stem of the tree just above a bud, to a low height, between 26 to 30 inches above the soil line. See if any branches are above the height of 30 inches, and cut them flush to the main stem. In case of branches that are between 15 to 30 inches high, just trim them, leaving small spurs behind.
Towards the end of June, select either 3, 4, or 6 branches that grow out from these spurs, at an angle between 45 to 60 degrees to the horizontal, and trim them to one-third their length. They should be evenly spaced from each other, both in height and width. A 6-inch spacing height-wise between them is ideal. These branches form what is known as the 'scaffold whorl' of the future tree. If you don't find any suitable branches to select as the primary scaffolds, then simply cut off all branches close to the stem, and wait for a year.
In the first dormant season, i.e., one year after planting, observe the growth of the tree. If you could not select the primary scaffolds the previous June, then you can do so now, and cut off all the other branches very close to the stem. If you have already selected the scaffolds the year before, then cut off all the branches that are growing above them, very close to the stem. Do not cut off the branches growing below the primary scaffolds completely; just trim them, leaving an inch of spur behind. This encourages the growth of the stem. Trim the height of the stem by about 18 inches. If any one of the primary scaffolds is growing vigorously, then cut it such that it is proportional to the others.
Man cutting branch
In the second dormant season, observe the primary scaffolds for branching. Completely cut off any branches that are within a distance of 10 inches from the main trunk. Trim the remaining branches on the scaffolds to a couple of inches in length. Again, trim the stem by about 18 inches from the top, which will encourage bushy growth.

You can also select newer scaffolds, by observing upward-sloping branches that have grown at an equal distance from each other and also from the primary scaffolds. This will make the tree grow in a vase-like shape with multiple scaffolds (shown in the image on the right). Trim the branches growing below the scaffolds, leaving only small spurs. The scaffolds should be selected in such a way that they provide a strong structure for the tree, allowing it to bear heavy load in the future. Allowing only a few branches to grow, while trimming off all the others, allows sunlight and air to reach the innermost branches.
From the third dormant season and after, keep the pruning only to a minimum. Cut off all dead, diseased, and undesired branches that grow inwards, thus allowing sunlight and air to penetrate the interior of the tree. Also, remove all branches that grow vertically from the scaffold, as they block light to the tree's interior.

Branches growing downward produce little, if any yield of plums, and they should be removed. Trim all the limbs regularly, to encourage newer growth and better yield. Pruning should always be done after harvesting is over. The ideal time for this is late winter to early spring. Harvesting in summer is generally not advisable, as the branches are difficult to reach. Pruning in summer has a dwarfing effect, and has more chances of damaging the tree. This is especially true for younger trees, while the established ones are not as affected. Moreover, when the plums first start appearing, thin them manually to space them out evenly and make them grow larger.
► Before pruning, always keep an eye out for the weather forecast. Pruning should not be done in humid conditions, as this encourages the problem of fungal growth.
► The pruning cut should always be sloping, to ensure that moisture trickles and falls off.
► When cuts are made close to the stem, apply a healing compound to encourage faster healing.
► The weight of the fruits during summer will spread out the tree even more, and if pruning is done improperly, branches may snap under the load.
► If branches are growing too close inwards, blocking off light, this will be indicated by discolored inner leaves and plums.
► If the tree reaches 8 feet in height, trim it such that it is only about 3 feet taller than the top branches.
► Sterilize your pruning equipment before the job, which will prevent the spread of infection.
The main purpose of pruning the Santa Rosa plum tree is to getter a better yield of plums and enable them to be harvested by hand. However, if pruning is done incorrectly, it can harm or even cause the tree's death.