Pruning plum trees isn’t terribly complicated, but there are still right ways and wrong ways to go about it. The time of the year is important, the climate the trees are growing in can be a factor, and whether you are talking about fruit-bearing plum trees or flowering plum trees can make a difference in the pruning requirements as well.
Pruning Flowering Plums
Flowering plums are often pruned with the shape of the tree in mind, or to maintain a certain height. In the case of flowering plums, pruning is often done for aesthetic purposes. It’s important, however, that when pruning a plum in bloom, the health of the plant is taken into account as well. This usually means cutting away some inside branches to allow for improved air circulation through the remaining branches.
It’s all too easy to make a branch shorter by cutting it back. If you cut it back too much however, there aren’t that many ways to cut a branch longer. You’ll probably have to wait a season for your mistake to be undone. If you’re pruning a flowering plum to a certain shape, and that shape is symmetrical, it’s a good idea to step back from time to time and observe the state of your progress. A lopsided-looking tree is often less attractive than one that hasn’t been pruned back at all. The best approach is to snip back a little from the ends of the branches, step back periodically, and see which branches need a little additional work.
Dead or damaged branches should be cut back to the trunk. Small branches can usually be taken care of with a hand pruner, but dead or damaged branches that are large in diameter should be removed using a pruning saw or lopping shears to ensure a clean cut. A ragged cut, which can result from trying to cut off too large of a branch with hand pruners, could harbor disease or provide an access point for insects. Any time you come across two branches that rub together or cross over one another such that there is a possibility they could rub together, one of the boughs should be cut back or removed. If large branches are removed, or the top section of the trunk has to be removed for any reason, it’s usually a good idea to cover the cut with a protective seal against insects and disease.
Pruning Fruit-Bearing Plums
The main purpose behind pruning plums that are fruit-bearing trees is to enhance or maintain fruit production. This means allowing sunlight access to any branch that is apt to set fruit, which usually means most branches on the tree. Opening up the tree with this in mind is also good for its health, in the same way it was in the case of the flowering plums, as a more open shape encourages good air circulation. If enough interior branches are not cut away, you could easily end up with a tree whose fruit, while large in size, is growing mostly at or near the top of the tree, where the sunshine is.
A common mistake made by many is to prune a fruit-bearing plum at the wrong month. People see apple growers pruning back their apple trees in the dead of winter or very early in the spring. They then assume that all fruit trees should be trimmed at this time of the year, when the plant is still dormant. The fact is plums should be trimmed in mid to late spring – in early June, for example. One reason for doing this is if a plum tree is pruned back too early, or during the winter months, they are more susceptible to silver leaf disease.
Pay particular attention to the lateral branches, those that are growing horizontally out from the trunk. These will eventually become the fruit-bearing ones, or more precisely those from which the fruit-bearing spurs will grow. These lateral branches can usually be shortened by about a third. There is no point in leaving the tips of the branches intact, as the tips will never produce fruit. By cutting them off, more energy will be directed to the fruit-bearing spurs.
There is another difference between pruning plums and pruning other types of fruit trees. Fruit-bearing plums can and should be pruned a second time each season. They should be pruned a second time not long after the fruit has been harvested. During this second pruning, new shoots which are unlikely to ever produce fruit should be pinched out. These shoots would usually form inner branches that would have to be pruned out in any event. The fruit-bearing shoots or spurs can be pruned back again slightly to encourage new growth for the next growing season.
Prune in June, cut out interior branches, nip off new shoots and tip, and your plum tree should stay healthy and produce abundance of tasty plums.