Arborists reveal when to prune a birch tree to keep it healthy and beautiful, plus when not to trim

Birch trees are magnificent trees to have in any garden. While they bring charm, color and character to a space, they have specific pruning needs. You need to know when to prune a birch tree as getting it wrong can threaten the tree’s health.

That may sound daunting. However, there are only a few key rules about when to prune trees. Birch trees do not want extensive, regular pruning. Indeed, they prefer small-scale pruning, which is required during their dormancy in late winter.

In this guide, experienced arborists reveal when to prune a birch tree and why they need trimming to help you have healthy, beautiful trees for years to come.

Why and when to prune a birch tree: what the arborists say

Birch are desirable trees that bring texture and seasonal interest to any landscape and different species are suited to many backyard ideas. Most people think of the classic birch tree with white bark, but there are also varieties with red, peeling bark and upright or weeping growth habits. No matter which of the 60-plus birch varieties you have, they all need pruning at the right time of year.

Why prune birch trees?

Birches are often fast-growing trees that bring beauty. However, they don’t always have a huge lifespan and commonly only reach around 30-40 years when grown in backyards. Pruning can be one way to help improve that lifespan, maintain a healthy structure, and also protect your property from future damage.

‘The most important reason to prune a birch tree is to improve its structure and mitigate the risk of future storm damage,’ says Mason Hanrahan, a certified arborist and president at Tim-O-Tree. ‘When large limbs or branches break, they can leave significant damage, which may be severe enough to harm the tree’s viability.’

It is also important to prune dead or diseased branches to keep the tree healthy, especially if it has been affected by the bronze birch borer. This native North American pest has a huge impact on trees. Bronze birch borers leave dead branches in the upper canopy that need removing.

‘It is crucial to have the deadwood pruned out ASAP to prevent the spread of the bronze birch borer insect to the rest of the tree,’ warns Kaustubh Deo, president of Blooma Tree Experts. ‘Once more than 25-30% of the canopy is dead, it's unlikely the tree will recover.’

Mason Hanrahan

Mason Hanrahan is an ISA-Certified Arborist (ON2491-A) and Qualified Tree Risk Assessor. He practices arboriculture in Ottawa, Canada, focusing primarily on tree removal and tree risk mitigation. Mason has been running Tim-O-Tree since 2018 and loves sharing knowledge and educating the public about trees.

When to prune a birch tree

There are important reasons to prune birch trees. However, pruning must be done at the right time and cautiously to avoid stressing the tree and causing harm.

The best way to avoid making tree pruning mistakes that can damage a tree and leave it susceptible to pests and diseases is by understanding exactly when to prune a birch tree and only heading out with the pruning tools at the right time of year.

So when do the experts recommend the best, and worst, time to prune birch trees?

‘Prune birch trees in late winter about one month before bud swell,’ says Scott Seargeant, a consulting arborist and owner of Seargeant Landscape & Arboriculture. ‘Very light pruning (two or three small branches) is permissible in summer, but do not prune birch trees in late summer or fall.’

Also do not prune in spring, as it will actively harm birch trees. ‘They are pumping materials through the xylem (and phloem), if pruned, they will “bleed” excessively, potentially attracting disease and insects,’ adds Scott Seargeant. In particular, spring is a prime time when bronze birch borer can be attracted to fresh pruning wounds.

Any steps to prune birch trees for structure are best done when the tree is young. For example, if the tree has two dominant leaders, that can cause both to be weak and at risk of snapping in storms. Such trimming is best done when the branches are younger and less than one inch, meaning the tree branches can be pruned easily and with smaller cuts that are quicker and easier to heal.

‘Waiting until the tree is mature means that the pruning wounds will be much larger,’ warns Mason Hanrahan. ‘As with people, the larger a wound to a tree, the greater the risk of infection; larger pruning wounds take longer for a tree to seal, meaning the window of opportunity for a fungus to infect the wound and begin rotting it is longer.’

Even though the dormant season is recommended as the best time to prune birch trees, Kaustubh Deo advises examining the tree in the fall. Inspecting a birch tree before the leaves have fallen makes it easier to spot the dead branches to target when pruning birch trees in winter.

Scott Seargeant

Scott Seargeant is an award-winning international consulting arborist and owns a full-service landscape installation company. His expertise lies in diagnosing tree conditions, providing treatment, and recommendations, selecting appropriate trees for planting, and offering guidance on post-planting tree care

FAQs

Can you prune birch trees in spring?

It is not advisable to prune birch trees in spring. It would be a pruning mistake to trim at this time of year as the birch tree would bleep sap heavily and be at increased risk of pests and diseases.

Is pruning birch trees in summer OK?

You can do small-scale pruning of birch trees in the summer. Ideally, wait until late summer, when the sap flow from cuts will be lower than early in the season and there is less risk of pest problems. Summer can be a time to remove any dead, diseased, or damaged branches.

Picking when to prune a birch tree can help extend your tree’s life, as they suffer if you trim too regularly. Scott Seargeant describes them as ‘daintier than most other trees’, and birches can react badly to pruning. He warns: ‘Birch trees in warmer climates do not live very long, even shorter if pruned too often.’ The lesson to take away is always to be cautious when pruning birch trees and only trim when vital.