02/13/2016
How and when to prune just about everything in your landscape.
A good starting point for pruning any plant is to remove dead, diseased, or damaged stems as soon as you see them. Dead stems attract insects and invite diseases to develop.
Also remove crossing branches, water sprouts (vigorous upright growing shoots that form on trunks or side branches), and suckers (vigorous shoots that develop near or from below ground).
Spring-Flowering Trees and Shrubs
Early-spring bloomers, such as lilac, forsythia, and rhododendron, bear flowers on wood formed the previous year. The best time to prune them is late spring -- immediately after they finish blooming. If you prune them later in the growing season or during winter, you'll remove flower buds and decrease the amount of spring bloom.
To keep spring bloomers flowering vigorously, remove some of the oldest shoots all the way to the ground. This allows younger stems to grow and bloom.
Summer-Blooming Trees and Shrubs
Plants that bloom in summer, such as potentilla, butterfly bush, and crape myrtle, produce their flowers on new growth from the current season. Prune them in winter while they're dormant, or in early spring just before they push out their new growth. You can even cut them all the way to the ground in late winter, and they'll still bloom that same summer.
Most hydrangea types -- pink, blue, or white mopheads and lacecaps, or oakleaf forms -- bloom on old wood. Prune these types of hydrangeas before midsummer. If you prune them in winter or early spring, you'll be removing flower buds.
With newer reblooming types, such as the Endless Summer Series or Let's Dance Series, which bloom on new growth as well as old wood, timing of pruning is less critical. Even if you cut off some of the flower buds by pruning the old stems, the plant will bloom on the new growth.
White-flowered paniculata (such as the varieties 'PeeGee' and 'Limelight') and arborescens (including 'Annabelle') types flower on new wood, so they can be pruned any time other than just before they bloom.
Shrubs Without Showy Blooms
Cut back shrubs grown primarily for their foliage, such as barberry and burning bush, almost anytime except in late autumn. New growth that starts after late-season pruning won't harden off properly before winter. If you want to do major pruning, it's best to cut the shrub back when it is dormant in winter.
Clipped Hedges
Shrubs such as boxwood and privet are often sheared to form a hedge. To maintain a solid wall of green, shear the new growth frequently during the early part of the growing season. Keep the top narrower than the base so that the upper branches don't shade the lower ones. Stop shearing the hedge approximately six weeks before your area's average first frost.
Roses
Treat climbers and old garden roses that bloom only once per year the same as other spring-blooming shrubs: Pruning after they finish blooming.
Repeat bloomers, including hybrid teas, floribundas, grandifloras, miniatures, and modern shrub roses are pruned mostly to shape the plant or to remove winter-damaged canes. If they become overgrown, cut them back in early spring.
Deciduous Shade Trees
Prune shade trees such as oak, linden, and ash when they are dormant in winter. It's easiest to see the branching structure at this time of year, and you're less likely to spread diseases through the pruning wounds. As with nonblooming shrubs, avoid pruning them late in summer.
Broadleaf Evergreens
Most broadleaf evergreens, including holly, mahonia, and some types of magnolias, need little pruning. The best time to prune them is in early spring, just before they put on their growth spurt. You can do minor shaping and pruning at other times of year, too.
Needle-Leaf Evergreens
Most trees and shrubs with needlelike or scalelike foliage (spruce, juniper, cypress, arborvitae, fir, yew, Douglas fir, and false cypress) are best pruned early in the growing season.
Avoid cutting back into wood that has no green needles; it may not sprout new growth.
Pines
True pines are more particular about their pruning needs than other needle-leaf evergreens. Pines form buds only at branch tips before the stem becomes woody.
For best results, prune pines only in the candle stage -- before the new shoots turn woody and before the needles have fully expanded. Prune only a portion of the new growth, removing up to half of the expanding candle.
