When and How Should I Prune My Plum Tree?

Pruning plum trees incorrectly — or at the wrong time of year — is one of the most common ways to introduce serious disease into an otherwise healthy tree. Unlike apples and pears, plums must never be pruned in autumn or winter. The timing rule for plums is non-negotiable: prune in summer, when the tree is growing actively and can seal wounds quickly, and when the spores of silver leaf and bacterial canker are at their lowest levels in the environment.

When to prune plum trees

The correct window for pruning plums is from late May to the end of August. The ideal is late May to early June for formative pruning on young trees, and immediately after harvest (usually August) for established trees. Pruning at these times allows the tree to callus over wounds rapidly — the growing season stimulates healing — and coincides with the period of lowest silver leaf spore release. Never prune in October through March, even to remove dead wood, unless there is an urgent structural risk.

Pruning established bush or half-standard plums

An established plum tree needs only moderate pruning each year. Remove: (1) dead, diseased or damaged branches, cutting back to healthy wood, (2) crossing or rubbing branches that abrade one another, (3) branches growing into the centre of the tree that reduce light and air circulation, and (4) any very long, whippy new growth that unbalances the structure. Aim to maintain an open bowl shape with good light penetration. Resist the temptation to shorten all new growth — plums fruit on both old spurs and young wood, and excessive shortening reduces the crop.

Pruning fan-trained plums

Fan-trained plums require more regular summer pruning to maintain their flat form. After fruit set, remove shoots growing directly toward or away from the wall, shortening remaining sideshoots to five or six leaves. After harvest, shorten these further to two or three leaves. Retain well-placed young shoots as replacements for older fruited wood. Tie in all retained shoots to the support wires.

Making clean cuts

Always use sharp, clean secateurs or a pruning saw. Cut just above a bud or branch junction — do not leave stubs. On cuts larger than 2 cm in diameter, applying a wound sealant can help protect against silver leaf spore entry, though evidence for its effectiveness is mixed. Clean tools with methylated spirit between trees to prevent spreading disease.

Dealing with dead wood and suckers

Remove dead branches at any time of year if they present a structural hazard — the risk of leaving a heavy dead limb over a path outweighs the disease risk of an out-of-season cut. Remove root suckers at any time by pulling or cutting them off at their source rather than cutting at soil level, which encourages regrowth.