Tropical Style

How & When to Prune a Plum Tree

Plum trees do best when grown within U.S. Department of Agriculture plant hardiness zones 5 through 9, although many varieties will bear the colder temperatures of zone 4. Irrespective of where they’re grown, plum trees need annual pruning. The two most important facets of pruning a plum tree are how it is pruned — for shape and for return — and when it is pruned. Since pruning and fungal disease go together with the plum tree, not only is it vital that you prune to allow sunlight to penetrate the tree, but pruning at the correct time is essential.

Time Frame

The best time to prune the plum tree is in the middle of June until August. Choose a period when there is no rain or fog in the prediction as heavy humidity in the air following pruning makes the plum tree susceptible to the fungal pathogen which causes silver leaf infection (Chondrostereum purpureum).

First and Second Year Pruning

Pruning the youthful plum tree is easy. Wait until new growth is 3 inches long. Cut the main stem back until it is 2 feet tall, making the cut just above a bud. As soon as you’ve trimmed the height, even in case there are competing leaders, or stems which are very close to the main stem, cut them off entirely flush with the main stem. From here you will want to choose four lateral branches which are evenly spaced around the tree and remove all others. These four divisions are known as the plum tree “scaffold whorl.” This pruning types the tree structure. At the tree’s second year, cut back each branch of the scaffold whorl to 10 ins and prune back the main stem by around 18 inches.

Third and Subsequent Year Pruning

In the next year you will want to create additional scaffold whorls, removing divisions until there are 18 to 24 inches of space between each whorl. Trim back the top whorl to ensure that every division is 10 inches long. The tree should be shaped somewhat like a Christmas tree, with the very best branches shorter than the bottom branches. Cut back the main stem by around 18 inches, again making the cut just above a bud. In following decades, create additional scaffold whorls until the tree reaches the desired height.

Overall Strategy

No matter the era of the tree you will find regular jobs to perform with each pruning. Basic pruning jobs include cutting out dead and damaged wood and removing any sections that cross over the others, as well as removing suckers — youthful growth in the soil, the lower trunk or that grow right up on the limbs. If the plum tree is 8 feet or smaller, cut the main division back so that it rises 3 feet above the top set of divisions.

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