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WHEN TO PRUNE

Basic Timelines

Maureen Sexsmith-West

ISA Certified Arborist, PR4600A


In tracking the views on my various blog posts – the most popular by far are the ones with the ‘how to’ tips. Your wish is my command, here is the first of a series of posts for DIYers.

There are emergency situations where these basic guidelines do not apply. If you follow these simple rules, your trees will thank you. Knowing why your tree is showing dieback, wilt or leaf changes is the first step. There can be a wide range of contributing problems – drought, insects, diseases, construction damage. Our Certified Arborist offer experienced diagnostic services about problems affecting our region. Once you know the cause – a program of maintenance can be recommended. Pruning is just one possible solution that can help preserve and improve the health of your tree.

ANY TIME: Removal of dead, diseased or broken branches should be done as the need arises (with the exception of season specific trees such as Elms, Birches/Maples see below).

NOT AT ALL: During bud break – this will vary depending on the tree species. Temperatures below -16 degrees. It is also not recommended in high wind conditions – you have little control over the direction the branches will fall and tearing/peeling is more likely to occur. See Fall also.

LATE SPRING (May/June)– This is the ideal time for shaping of newly foliated hedges or live tissue cuts on evergreens. This is the time for planting – trees and shrubs become available at local stores. The arrival of insects tends to arrive in conjunction with flowers and foliage. Identification of the pests is key to making control choices. Spraying is not always necessary. The key is early detection to achieve controls and understanding whether it is a threat to the health of your plants or just a temporary annoyance.


SUMMER (July/August) – BIRCH AND MAPLE should not be touched until July / August. The reason for this is extensive movement of the nutrients within these types of trees to promote reproductive development. Pruning cuts made OUTSIDE of this time frame will result in excessive sap flow that releases pheromones which attract pests, diseases and stress. Attending to post flowering shrubs such as spirea or common lilac help maintain vigor and form. Removal of water sprouts on fruiting trees will redirect energy where it is most needed.

FALL (September): Removal of live tissue before the tree has had a chance to store it in the trunk and/or roots will set it back for next season. Avoid making major pruning cuts on any woody plant at this time. Once the leaves have turned and are falling off, you can be confident that it has stored the carbohydrates and starches it produced during the growing season. Concentrate on fall fertilization, applying mulch and deep watering in anticipation of winter.

EARLY WINTER (October to January)

Once the leaves have dropped, the dormant period is the best time to prune deciduous trees. Be aware that there are some exceptions which as regulated or season specific.

ELMS: In an attempt to control the onset of Dutch Elm Disease, the province has implemented a pruning ban which only permits the pruning of elms from October to March.


LATE WINTER (February to April) – Lindens, apples, plums, cherry, schuberts, mayday, tree lilacs and mountain ash are best pruned at this time to affect fruit production and flowering.

SPRING (April/May) – this is the time the tree is breaking bud – NO PRUNING SHOULD TAKE PLACE other than dead wood removal on trees. This is a good time to rejuvenate old shrubs. Also a good time for root pruning. Concentrate your efforts on planning, getting estimates, fertilization and watering.

WATCH FOR FLAGGING – this is the unseasonal changes in foliage evidence by wilting, drying out or browning off. This an indication of either insect and disease damage which should be dealt with immediately to prevent spreading. It is also another indicator of mechanical or structural damage – essentially the branches has been broken of injured. And should be pruned away to the most appropriate lateral behind the injury.


Evergreens – remove disease materials during the dormant season. Check any flagging branches as they occur and remove immediately if infected to prevent further spreading.

Pruning cuts should always be made to a bud or branch 1/3 the size of the branch it is attached to so it can manage the flow of vascular fluids. DO NOT LEAVE STUBS or make TOPPING cuts. During the summer months, ALWAYS disinfect tools when working on diseased trees. Watch for our post on pruning techniques soon.

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