A plum tree is pruned in July and August, not in winter. Silver leaf spores are in the air from September to May and get in through fresh cuts, and the same months are the riskiest ones for bacterial canker. A young tree that still needs its framework is the exception and is pruned as the buds break in spring. Timing decides more than cutting technique.
Winter is right for apples and wrong for plums
An apple tree can be pruned during dormancy, from November to early March. Do the same to a plum tree and you open it to two diseases.
Silver leaf: The fungus Chondrostereum purpureum releases spores from September to May. They get in through wounds, above all pruning cuts. The leaves on the infected branch take on a silver-grey tone and the branch dies back. There is no cure, only prevention.
Bacterial canker: Pseudomonas syringae enters through wounds and through the leaf scars left at leaf fall. The cankers show in spring as sunken, dead bark. The wood is at its most resistant in July and August.
Both are favoured by damp and cool conditions. Prune on a dry day, ideally with a dry forecast for the next 2 days. The same timing rule applies to cherries and the rest of the stone fruit.
The pruning year month by month
| Period | What happens in the tree | What you do |
|---|---|---|
| November to March | The tree is dormant and wounds do not callus over. | Nothing. The season that works on apples is the worst one on plums. |
| April and May, at bud break | The sap rises and the tree answers with new growth. | Building the framework of young trees for the first 4 years. |
| June | The fruitlets sit close together and the new shoots are still soft. | Thinning the fruitlets. Soft shoots are pulled off by hand. |
| July and August | Shoot growth slows and a cut surface dries within hours. | Maintenance and renewal of established trees. |
| September | The spore season has started and healing is slower. | Small cuts only, early in the month, in dry weather. |
| October | Leaf fall leaves thousands of leaf scars. | Nothing. Put the secateurs away. |
The summer window is two months, not three
The usual rule of thumb for fruit trees names the three high summer months. On plums only the first two hold. September is the weak link, because the silver leaf spore season starts then and cut surfaces dry more slowly with every passing week. In most of the UK and northern Europe, July and August are the two months you can rely on.
Our rule: put the heaviest cuts in July, finish in August and keep September for what you forgot. On an apple tree you can use the whole of high summer and the winter as well. On plums you have 2 months in practice, and that is the reason to plan ahead.
Plums bear fruit on younger wood than apples
On an apple tree the fruit sits on short fruiting spurs, which form on wood that is 2 years old and older. Plums bear on a mixture: on one-year-old and two-year-old shoots and on older branches.
Cut back every shoot tip, the way you do when thinning fruiting spurs on an apple tree, and you remove next year's crop. The decision rule becomes: take out whole branches where the crown is too dense, but leave last year's shoots on the branches you keep. A tree that is never allowed to make new shoots stops cropping, which is a common reason why an old plum tree stands full of leaves and empty of fruit.
How to build up a young tree
The framework is built in spring, when the buds break and the leaves unfold. Growth is being pushed then, which is what you want at this stage.
Year 1: Leave the tree alone. The roots need to establish. Take out damaged branches only.
Year 2: Choose 3-4 main branches radiating from the top of the stem, evenly spaced around the tree. Grown as a bush, they sit about 75 cm above the ground. Shorten them by half and take the rest away.
Year 3: Keep the centre open like a goblet. Take out shoots growing inwards or straight up. A branch at less than 45 degrees to the stem has a weak attachment and tears loose under a full crop.
Year 4 onwards: The framework is done. Move pruning to July and August and make it lighter every year.
An old neglected tree is taken over three summers
A tree that has not been touched for ten years cannot be put right in a day. Every cut is a way in for silver leaf, so the number of cuts matters as much as where they go. We would rather take out two thin branches than one thick one.
Summer 1, July: Take out dead, diseased and broken wood. Leave everything healthy alone. The framework of the tree now becomes visible.
Summer 2, July or August: Open the centre. Crossing and inward growing branches come out, at most a fifth of the living branch structure.
Summer 3, July: Bring the height down. Shorten the tallest branches to an outward facing side branch that is at least a third as thick as the part you take away.
A large cut stays open longer. Shorten a branch in the middle, with no side branch to draw the sap, and the stub dies back and becomes a way in for the fungus. Once the crown lets light down to the ground you can sow meadow mix seeds under the tree instead of fighting the grass.
Suckers and shoots below the graft union
Almost every plum tree is grafted. The graft union sits just above soil level, and everything that comes from below it belongs to the rootstock, not to the variety you bought. Plum rootstocks throw suckers readily, sometimes some way out from the trunk where a root runs close to the surface.
Pull it loose, do not cut it: Dig down to where the sucker leaves the root and tear it loose. Cut it at soil level and you leave the dormant buds at its base, and next year two shoots come up instead of one.
Rub the buds off: Buds on the lower part of the stem are rubbed off with your thumb while they are still green. That way no cut is ever made that could be infected.
Walk a round once a month: From May to August one check a month is enough. A soft shoot comes away by hand, a woody one has to be dug out.
Thin the fruitlets so the branches hold
A plum tree regularly sets more fruitlets than it can carry. A branch that tears loose at its attachment leaves a wound that cannot be cut back neatly. Thinning is the only job on the list that makes no cut in the wood.
Thin in June, once the tree has dropped some fruitlets of its own. Leave one fruit every 5-8 cm along the branch, or a pair of fruits every 15 cm. Fruits resting against each other stay damp, and that is where brown rot usually starts. If you do not get the thinning done, prop the heaviest branches in July and August.
How much fruit sets is decided back at flowering in April and May. Plums flower early and depend on bees and bumblebees, so a strip sown with seeds for pollinators near the tree puts more insects in the air while the blossom is open.
Five mistakes we see most often
Pruning plums the way you prune apples: March works on apples. On plums the spores are moving and healing has not started.
Reading gum flow as proof of disease: Gum from the bark is common on all stone fruit and does not in itself mean the tree is infected. It points to bacterial canker only when the gum sits together with sunken, dead bark.
Painting the cut surfaces: Wound paint seals moisture against the wood. A clean cut in July dries within hours in open air.
Cutting off all of last year's shoots: They carry next year's fruit. Take out whole branches instead and leave the shoots on the ones you keep.
Making up ten years in one go: A hard pruned plum tree answers with water shoots. Three light summers beat one hard one.
Author: Emma Vogiatzi
Fact-checked by Erik Hoekstra
Last updated 2026-09-25