Spring is here and not only are we out enjoying the sun, many of us are itching to get into the gardens and start getting things ready for their impending bloom. But before you get a hold of those pruners or loppers, you need to know what should and shouldn't be cut....and when.
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 or below the 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.
Tip: 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 clematis, 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.
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.
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.
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.
Deciduous Fruit Trees
Apples (including crabapples), peaches, pears, plums, and cherries should be pruned in midwinter. Although winter pruning removes some of their flower buds, the goal in pruning fruit trees is to open up the tree to allow in more light for a better crop of fruit, rather than to get maximum bloom. Dormant pruning is especially important for apples, pears, and crabapples because pruning wounds during the growing season expose the trees to a bacterial disease called fireblight. To control the spread of diseases while pruning, dip your pruning shears in rubbing alcohol or a solution of one part bleach to nine parts water.
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.
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. As with broadleaf evergreens, you can trim a few branch tips in midwinter to take some greenery indoors.
Most perennial flowers look best if you remove faded flowers. This is called deadheading. As a bonus, many perennials will push out another cycle of blooms after deadheading. If Perennial flowers become too tall and leggy, or flop open in the middle, try shearing them back to 6-12 inches above the ground. This type of haircut causes them to branch and become stockier.
Deadhead annual flowers regularly to keep them blooming well. Removing the old flowers prevents them from setting seed and allows plants to put more energy into blooming. Some annuals such as petunias sprawl and develop bare stems at their bases. As with perennials, you can shear these rangy plants to force more compact growth and renewed bloom.
So there are the basics. I do not proclaim to be an expert by any means, but I love my landscape and have learned a lot along the way. If you have specific concerns or questions....those people who work at your local nurseries are a fantastic help to guide you in what to do with plants and trees in your local climate/zone.