When and How Should You Prune a Plum Tree?

Plum trees are stone fruits, and stone fruits follow completely different pruning rules from apples and pears. The critical distinction is timing: plums must be pruned in summer, not winter. Getting this wrong is one of the most common and costly mistakes in the home orchard. It can result in silver leaf disease killing entire branches — or even the whole tree.

Why Plums Must Be Pruned in Summer

Silver leaf disease (Chondrostereum purpureum) is a fungal pathogen that enters plum trees — and all other Prunus species — through fresh pruning wounds. The spores are released mainly in autumn and winter, peaking during wet cold weather. By pruning in July or August, during dry summer weather, you cut when spore counts are at their lowest and when the tree's active sap flow helps seal wounds quickly. Never prune plums between November and March unless it is an emergency.

What to Prune on a Plum Tree

Plums are vigorous and produce a great deal of new growth each season. The main tasks are: removing dead, diseased, or damaged wood; taking out crossing and rubbing branches; and thinning the canopy to let light and air reach the centre. Plums also throw up root suckers — vigorous shoots arising from below the graft union at ground level. Remove these with a clean cut as close to the root as possible; do not leave stubs as they will re-shoot.

Young plum trees can be trained to an open-bowl shape in the first three years, again pruning in summer. Established trees need only light annual maintenance once the framework is set.

Recognising Silver Leaf Infection

Silver leaf causes the leaves on affected branches to develop a silvery metallic sheen. If you see this, cut the branch back until you see clean white wood without any brown or purple staining in the centre of the cut. The staining is mycelium spreading through the vascular tissue. Sterilise your tools after every cut and dispose of infected wood well away from the garden. A tree with silver leaf in the trunk rather than isolated branches is usually beyond saving.

How Hard Can You Prune a Plum?

Plums respond vigorously to pruning with large amounts of new growth, which can become a new problem if cuts are too large. As a general rule, remove no more than a quarter to a third of the canopy in any single season. If the tree has been neglected and needs major work, spread the renovation over three or four summers rather than doing everything at once. Large wounds are also a bigger target for silver leaf — if you need to remove a large branch, do so in stages over two seasons.