For most trees in Ottawa the best time to prune is late winter, while the tree is dormant: you can see the structure, disease pressure is low, and cuts start closing as soon as growth begins in spring. The exceptions matter: do not prune oaks from April to July, prune spring-flowering trees right after they bloom, and remove dead or broken branches whenever you find them. In Ottawa, pruning done to good arboricultural practice needs no City permit.
From about February into early spring, most deciduous trees are dormant. With the leaves gone, it is easy to see crossing branches, weak forks and deadwood. Insects and fungi are inactive, so fresh cuts are less likely to be infected, and the tree starts sealing them within weeks once it wakes up. Frozen ground also means less damage to your lawn and beds.
Some trees need different timing:
The least good times are when leaves are coming out in spring, when the tree has spent its reserves and bark tears easily, and during leaf drop in autumn, when fungi are spreading spores. Avoid heavy pruning during a drought, too: a stressed tree copes badly with losing leaf area.
Less than people expect. A good rule is to remove no more than about a quarter of the living crown in a year, cut back to a branch or the trunk collar rather than leaving stubs, and never top a tree: topping causes weak, fast regrowth and decay that shortens the tree's life. Deadwood, crossing branches and weak forks come first.
Under Ottawa's Tree Protection By-law, pruning that maintains a tree's health and follows good arboricultural practice needs no permit. Heavy cuts, topping or root damage can still count as injuring a protected tree. A tree on the City boulevard belongs to the City: report problems to 3-1-1 rather than pruning it yourself.
Bisson Services prunes trees of every size across Ottawa and Prescott-Russell. See tree pruning, or call (613) 558-4806 for a free estimate.
Late winter, roughly February to March, for most deciduous trees. Oaks only in the dormant season, and spring-flowering trees right after they bloom.
No, not for pruning that maintains the tree's health and follows good arboricultural practice. Heavy cuts or topping can still count as injuring a protected tree.
Fresh wounds attract the beetles that spread oak wilt, a fatal disease confirmed in Ontario. Prune oaks only while dormant, never April to July.
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