Trees, Shrubs and Vines to Prune in Winter

When to prune depends on the plant species, length of the growing season, bloom time, and if new buds are formed on old or new wood. Wood is also pruned in two phases; on new growth to encourage the proper shape at maturity, and on mature plants to enhance their health, beauty and productivity.

When to Prune Trees

Generally, most woody plants should be pruned in late winter, when the days are starting to lengthen and get warmer, but before buds start to swell or new growth emerges. With deciduous plants, it’s also much easier to see what needs pruning when they’re bare. Choose a cloudy, gray day when the wood isn’t frozen but the sun isn’t warming the sap. This will minimize the inevitable sap loss, which will not permanently damage the tree.

Trees respond chemically to pruning by ‘walling off’ the injury. They developed this self-defense mechanism because natural breaks occur in predictable areas: the joints or crotches where small limbs join larger ones. There is usually a small raised ring of bark in these joining areas, known as branch ring collars. These contain high concentrations of the chemicals needed for walling off. If you make all pruning cuts just above these branch ring collars, the tree will create its own natural bandage.

The Right Tool for the Job

Scissors-like pruners are used on small stems and twigs. Long-handled loppers give good leverage on larger branches. Do not try to cut through a branch that is too thick for the loppers, or the tree could be damaged. Use a folding pruning saw; its narrow, curved blade also makes it easier to use with closely spaced branches. For big limbs, use an orchard pruning saw. A pole saw is basically a saw on a stick to allow you to reach higher branches. For your personal safety, never use a pole saw anywhere near power lines. Wear goggles to protect your eyes from sawdust.

If the tree is so big that you need to use a ladder or climb into the tree in order to properly prune it, hire an arborist. Your safety and well-being are worth the expense.

How to Prune Trees

• Remove dead, dying, diseased or damaged branches.
• Remove suckers emerging from the tree’s base.
• Remove crossing branches.
• Remove lower branches only if you want more headroom or for a better view of handsome bark.
• Thin out dense growth to allow more light and better air circulation to reach the center of the tree.
• Stand back and check for balance. If an area is still too dense, prune accordingly.

Pruning Larger Branches

Make an undercut in the branch 12 to 24 inches from the trunk. When the saw starts to stick, make a second cut through the branch an inch further out from the trunk. Cut it a third time just above the branch ring collar.

Pruning Shrubs and Vines

Generally, shrubs and vines that bloom in spring should be pruned in summer. Ones that bloom in summer are pruned in winter. Shrubs and vines should only be pruned for four purposes, so first determine what you intend to accomplish.

Enhance the Natural Form of the Plant

First cut out dead or damaged stems. Thin out branches rather than pruning the tips. Stand back and examine the plant from all sides, then remove branches that make the plant seem unbalanced. This technique works well with forsythia, azaleas, viburnums and other flowering shrubs.

Increase Flowering

Tip cutting on woody shrubs like roses, just above a strong bud, will enhance its growth and encourage lateral branching along the entire stem. Climbing roses that bloom once in spring should be pruned after blooming. Repeat bloomers that climb should be pruned of dead or diseased wood in spring and again in summer. Otherwise, it depends on where you are geographically: Northerners should wait until early spring, when buds are just swelling. In milder climates, during the winter months is best.

Control the Plant’s Size

Some plants, such as wisteria, grow so exuberantly that they benefit from a hard pruning in late winter, before the buds swell. This aggressive vine also benefits from several mini-prunings throughout the growing season. For flowering shrubs like forsythia, follow their natural shape. Don’t take tip cuttings, cut them off at the base.

Rejuvenate an Old Shrub

Some long-lived shrubs get overgrown or spindly. By taking a pruning saw to the dead stems at the base, and then cutting the healthiest branches to about 24 inches, you may be able to rejuvenate the plant. Feed it with a slow-release fertilizer and keep it well-watered to encourage new growth. It may take it a year or two to fill out and resume flowering.

Plants to Prune in Winter

Vines:

• Bittersweet (Celastrus spp.)
• Clematis (late blooming varieties)
• Dutchman’s pipe (Arstolochia durior)
• Honeysuckle (Lonicera spp.)
• Hops (Humulus lupulus)
• Retwig dogwood (Cornus sanguiea)
• Silver lace vine (Polygonum aubertii)
• Wisteria (Wisteria spp.)

Shrubs:

• Althaea (Hibiscus syriacus)
• Beautyberry (Callicapa spp.)
• Butterfly bush (Buddleia davidii)
• Crape myrtle (Lagerstroemia spp.)
• Spirea (summer-blooming varieties)

For more information on how to keep your winter garden protected and productive, please read Protect and Maintain Plants in Cold Climates, and Keep Your Garden Growing Through the Winter.