Deciding when to prune/trim is confusing to many people because there is no one-size-fits-all answer and even the experts can’t always agree. Yet, it is the most commonly asked question of gardeners, landscapers and arborists! Pruning of live branches is not as critical as many people think, but it is worthy of discussion.
The Best Times for Pruning: (the opposite of Part 1; Worst Times)
- A mild, dry and seasonal day
- When the plant is healthy and hasn’t recently been disturbed by construction, storms and/or heavy pruning
- It depends on how much you plan to cut off;
A Heavy Trim >50% cutbacks of shrubs, the best time is late winter, early spring
A Medium Trim ~25% maximum amount to remove annually, early spring and summer
A Light Trim <15% anytime of season
- It also depends on whether or not you will miss the full flower effect;
If you won’t miss some of the blooms, prune anytime of season
For plants that bloom on current season growth, in late winter, early spring
For plants that bloom on previous season growth, right after bloom
- Lastly, Dead branches can be pruned anytime!
In general, the optimal times for ornamental tree and shrub trimming is early spring and summer and those should be the go-to times if you are unsure. Don’t let timing keep you from grabbing your pruners if a haircut is truly needed and you just can’t wait!
If you are trying to figure out the best time to prune/trim, start first with the worst times to prune (because more experts agree on these) and work backwards from there.
So, what are the worst case scenarios in pruning at the ‘wrong time’?
- Loss of flowers/fruit
- Health decline/injury
One important point is that pruning at the “wrong” time of year probably won’t kill your tree or shrub, but it may weaken it in the long run. Indeed many plants are trimmed at less than ideal times and yet they survive.
The Worst Times for Pruning:
- In the rain. Many bacterial and fungal diseases are spread during cold or hot wet weather and fresh cuts make easy access.
- During a severe drought, or flood like conditions. Energy is precious at these times and taking off branches is adding additional stress.
- When current or upcoming temperatures are extreme. Fresh cuts are open, exposed living cell tissue that can dry out or freeze and the wood surrounding the cut can dieback.
- When your tree or shrub is unhealthy. Wait for it to recover by giving it time and treatment (if necessary) before pruning.
- After storm damage, root injury (like construction) or heavy pruning. Plants need time to recover from loss of branches and roots before any trimming is done.
- Right before bloom. Does this really need explaining? Well, OK, maybe flowers and fruit aren’t your first priority.
To be continued in When To Trim, Part 2.