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Winter is the best time of the year to prune many deciduous plants, from mid-November to early March, depending on the temperature. With this year’s early freeze in November, low temperatures and significant snowfall, we have decided to wait for a mild, sunny day in March.
Why prune in the winter
Pruning in the winter, the dormant season, invigorates many trees and shrubs. Plants have extra root and energy reserves so that they can support new spring growth on the remaining branches. Plus, with the leaves gone, one can clearly see the plant’s branching structure. In the winter, there is also less chance of transmitting diseases from one plant to another or attracting insects to fresh prune wounds.
What to prune in winter
- Summer-flowering shrubs and vines, including hydrangea, rose-of-sharon, itea, hypericum and most spireas. You will not destroy the coming season’s flower buds since they will develop on new growth that occurs after you prune.
- Trees that are prone to disease and insects and that ‘weep’ when pruned. This includes oaks, apple, pears, maples, birches, dogwoods, walnuts and elms.
- Bush roses (hybrid teas, floribundas, grandifloras, and miniatures) to repair winter damage and shape plants to induce flower-bearing shoots. These types of roses bloom on new growth. Most of the new hybrid roses, including the Knock Out series, fall into this category.
- Climbing roses, which should have only winter-killed parts removed at this time, because blooms typically develop on shoots arising from old wood. Any cane that has lived through the winter is a potential source of flowers.
- Caution – Spring flowering trees and shrubs must be pruned after they have bloomed, otherwise, you’re cutting off this season’s flowers. Wait to prune lilacs, viburnums, crabapples, magnolias, dogwoods, forsythia, flowering quince and weigela. It’s best to prune these plants right after their flowers fade and before their new growth begins.
Proper pruning develops a framework of strong branches that increase air circulation and light penetration within the crown, improving overall healthy. Keeping foundation plantings in scale with a house and maintaining a plant’s natural shape enhances the beauty of a landscape.
How to prune
- Have a clear purpose in mind with what end shape you desire of the plant’s structure. Strive for a naturalistic form.
- Remove all undesirable branches, which include dead, diseased, crossing and rubbing branches. Start with the largest branches and move to the smallest. Prune back to a live bud that is facing outward so that the branch will grow towards the exterior of the plant.
- Next remove suckers or water sprouts. Suckers are whip-like branches with smooth bark and very few leaves that grow from the base of a plant. Water sprouts are similar naked-like branches, usually growing at right angles from existing limbs.
- Next, selectively remove branches to thin the plant and accentuate its natural shape. Cut branches back either to the base or branch of the plant or to an existing bud to avoid leaving an unsightly stump that can harbor disease or insects.
- Periodically, stand back and take a look at the results, a distant view of your work will indicate when it’s time to stop. You can always take more off but once a branch is cut, you can’t put it back on.
- Never remove more than one-third of a plant in one season, and do not give plants an unnatural balled or flat shape. A badly overgrown shrub may take more than one year to bring under control, but it can be done.
- Multi-stemmed plants like kerria, mockorange, weigela, forsythia and red-twig dogwood can be renewed by removing one-third of the oldest stems entirely every one to two years to 2” above the ground. This promotes new growth and helps to maintain a proper size. Twiggy shrubs that get overgrown can be rejuvenated by cutting all of the stems to two to four inches from the ground. Spirea, deutzia, potentilla and privet are shrubs that benefit from a periodic rejuvenation pruning.
- Trees and shrubs with heavier, more structural branches, like viburnums and crabapples, cannot be pruned like the above plants. For these plants, unwanted wood – whether it is dead, crossed or too dense – should be pruned back to the main branches, not to the ground.
- Note – Trees and shrubs do not need to be pruned routinely every year. Evaluate your garden each fall and winter and determine which plants require your attention. And again, wait to prune spring-blooming trees and shrubs until after they bloom.
Sources
We referenced multiple horticulture sources for this newsletter article. Please refer to the following publications or websites for additional information and instructional pictures about winter pruning and pruning in general.
Reprinted from MODE Landscape Design Vol 15: The Effects of Winter, March 2014
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