The Right Time to Prune Trees and Shrubs
Frederick County Master Gardener Program
The right time to prune depends on what it is you're pruning, and why (you really didn't expect a simple answer to this question, did you?) Pruning serves lots of different purposes, some of them seemingly contradictory. You prune to control
growth, and you prune to encourage growth. You prune to stimulate flower and fruit formation, but pruning at the wrong time or in the wrong manner can eliminate flowers and fruit entirely, and so it goes. But don't despair: there are some simple, common-sense rules to
Take spring-flowering shrubs and small trees like lilacs, rhododendrons, azaleas, and viburnums. If you prune them now, you risk removing flower buds and spoiling the spring show. Lilacs should be pruned after flowering by removing old stems
at the base to encourage strong new shoots. If you have to prune azaleas and rhodos to keep them in bounds, do this as soon after flowering as possible, because next year's blooms form during the summer. With all plants, it's better to choose varieties that will grow to fit
the space you have allotted them, and no more. Viburnums also form flower buds during the summer, and in this area, are often rank growers- prune after flowering, and choose your varieties wisely.
Fruit trees and their flowering relatives are traditionally pruned at this time of year. In this case, pruning is done to maintain the general form and size of the tree while providing an opportunity for new growth (and a continued supply of
fruit). The experienced pruner will strike a balance between preserving some of this year's flower buds, and thinking ahead to provide strong new branches for the coming years. Maples and some other trees should be pruned in spring or summer, not because of their flowering
patterns, but because if they are pruned now, they will bleed sap (think maple sugar). Many dwarf or slow-growing woody plants never need pruning.
You can - and should -- prune diseased or damaged wood at any time. If you're cutting off a diseased branch, make sure to cut back to uninfected wood -- you can usually tell by the color of the wood and bark what's healthy and what's not.
Choose the place to cut carefully - cut just above a new bud, and don't leave stubs or stumps which can serve as entry points for disease. Clean cuts, slanted away from buds on branches, or flush to the branch or trunk on larger limbs, heal quickly. In most cases, your goal
is to encourage the natural growth patterns of the tree, shrub, or vine that you're pruning. The hacked-off limbs perpetrated along public roadways to maintain clear utility lines are not a good model.
I've made pruning sound more difficult and confusing than it is. Unlike some other activities -- building a deck, for instance -- pruning mistakes grow back. It's far easier to learn pruning by watching an expert than by reading a
description, but there are many good books on pruning for orchardists and other gardeners - check the library or your local garden center. In the meantime, if you think about how your plant grows and why you are pruning it to begin with, you're already off to a good start.
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