15th December 2020

Pruning Plum Trees

If you’ve always been told to prune your fruit trees in winter, think again! Pruning plum trees are an exception to the rule.

When to prune plum trees

UK fruit trees tend to be pruned in the winter, while the tree is dormant, but not the plum. Pruning plums in the winter will put them at risk of silver leaf disease, a fungal disease that often affects trees of the Prunus species.

The best time to take on pruning plum trees is actually either in the early spring or late summer (or both). Young trees are best tackled around April while more established trees can be left until July.

How to prune your plum tree

As with all pruning, you should first make sure that your tools are sharp and well-maintained and that you can carry out the work safely.

You should also start with removing any dead, dying or diseased branches as they serve no purpose. Where a lot of pruning is required, this should be spread out over several years.

Apart from these basic guidelines, the specific pruning method you use will depend upon the shape of your tree.

The bush shape is by far the most common. The stem should be kept bare by removing suckers and rubbing out buds up to a height of 75cm (2.5 feet). The aim should then be to keep the centre of the tree open by removing any vertical branches and, where branches are rubbing, cutting back the one that is growing in the ‘wrong’ direction.

Over time, bush-shaped plum trees can grow to between 10 and 15 feet depending on the rootstock used.

Pyramid-shaped plum trees are kept to between 6 and 8 feet in height and should be pruned in both spring and summer to maintain their shape. In late July of their first summer, after the young shoots have stopped growing, shorten branches to 20cm (8 inches). Cut each branch back to a bud that is growing either downwards or outwards.

Cut side branches back to 15cm (6 inches).

In April, you can work on the central leader branch, shortening it by two thirds. Repeat this process every year until the tree has reached 8 feet (or 6 feet if on a Pixy roofstock). You can then simply cut back the leader each May by an inch to maintain the correct height.

In late June, remove any competing vertical leaders. Then, in late July, shorten the leader branches and side branches to 20cm and 15cm as before.

Choosing the best time to prune trees

Before pulling out the secateurs, it is important to time your pruning wisely. The best time to prune will depend on the species of tree and the purpose of your pruning.

Dead and dying branches should be removed promptly, regardless of the season. Even if these branches are safe they will take valuable nutrients from the tree and increase the risk of disease spreading to healthy parts of the tree.

For general pruning, some trees (e.g. apple, mulberry and red cedar) benefit from winter pruning, while the tree is dormant. Others (e.g. beech, acacia and alder) are best pruned in the late spring or early summer, once the leaves have hardened.

The Arboricultural Association have produced a list of the best time of the year to prune specific tree species.

How to prune a tree

Before you begin, make sure that you have a set of clean, sharp tools. You will need a pruning saw for branches thicker than 4 to 6 inches but smaller branches and shoots can be removed with loppers and secateurs.

You will then need to choose which branches to remove. Start with the dead or dying branches (crown clearing) before moving on to healthy branches. Look out for branches that are rubbing against each other and keep the branch that is going to maintain the shape of the tree you want. 

If you want to thin out the branches, don’t remove more than 20% in one season. This can stress the tree and will deprive it of food by reducing the leaf area.

To remove branches cleanly, first make a vertical cut halfway through the underside of the branch about 18 inches out from the trunk. Next, move slightly further out and cut through the entire branch from the top. Finally, make a 45 degree sloping cut from the raised area of bark next to the trunk. You want to leave a slightly-protruding area which will quickly form a callus. The slope helps to drain water away and prevent disease.

When pruning fruit and flowering trees, your aim is to stimulate new growth. You achieve this by cutting flowering shoots back to a bud that is growing in the desired direction.

While the above tips will help get you started, every tree is different and it takes dedication and patience to truly master the art of pruning.

Common problems with plum trees

Problems with plum trees often relate to neglected pruning. As plums will produce fruit with minimal help, they are often left to their own devices.

Eventually, the tree will become crowded and the fruit will only grow on higher branches. This is inconvenient and can also  lead to overladen branches which can break and fall.

In common with other fruit trees, bare patches can also develop on plum trees. You can sometimes stimulate growth in these areas by pruning right back to buds above the bare section. For larger branches, ‘notching’ can sometimes work. This involves removing a section of bark just above the dormant bud.

Plum trees can also be affected by several different pests including silver leaf disease (mentioned above), honey fungus, plum aphids, pocket plum and plum moths.

Over time, an unpruned plum tree can grow out of control. Are you worried about falling branches or having to climb ladders? Contact Kneebone Trees for a safe and effective pruning service. We follow the European Tree Pruning Guide.

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