Late winter is the perfect time for pruning most woody plants.
They're still dormant, you can better see what you're doing because your view isn't obstructed by leaves, and it's when plants heal fastest. If you're unable to prune before April 15, wait until July, which is the next-best time to prune.
There are two types of pruning - selective and rejuvenation.
Selective means what it sounds like: You select certain branches to remove, and you have a reason for doing so.
Rejuvenation pruning is the extreme cutting back of overgrown, unproductive shrubs, but plants must be healthy to withstand it. To rejuvenate, you have three options: Sever the whole plant at the crown, where the stem meets the roots; prune all the branches at unequal heights all at once, or prune a little each year over the course of a few years. The latter method is the least severe but requires the most patience. The first method is actually the best, but it requires a certain level of intestinal fortitude. Plants should be fertilized well after undergoing any rejuvenating pruning.
Broadleaf evergreen shrubs (laurels, rhododendrons, etc.) should undergo only selective pruning, and they can take it at any time of year.
Narrow-leaf (needled) evergreens should undergo selective maintenance pruning only. Always remove more from the top than from the bottom, which will allow sunlight to reach the base of the plant. Take care not to overshear or cut holes into narrow-leaf evergreens; with the exception of yews, they won't ever fill back in.
When it comes to hedges, there's only one basic rule: The bottom must remain wider than the top. If the plant thins out at the bottom, the only way to correct it is to cut the entire hedge down to 6 to 8 inches from the ground and wait for it to grow back. You don't want to go there.
When pruning shrubs and trees with thin branches, use pruners to remove dead wood, crisscrossed limbs and branches that are growing into the tree's canopy. But when removing a branch with a diameter of more than one inch, never make a flush cut, which would remove the branch collar and create a bigger wound. Instead, use your saw and the three-cut method (pictured at right).
Pruning notes and exceptions
For lilacs and similar spring bloomers, it's best to wait until after their flowers fall so as not to remove flower buds and spoil the season's show.
Forsythia should be pruned every year right after flowering.
Spirea and weigela should be pruned every two to three years.
Clethra and cotoneasters should seldom be pruned.
Butterfly bush (Buddleia) should never be pruned in fall, or it will die. Instead, cut it all the way to the ground every year in early spring.
Deadhead rhododendrons and mountain laurels only if they aren't full enough, and do it immediately after flowering. Waiting even a week will defeat the purpose, and the plants will remain leggy.
Hydrangeas are in a class all their own - actually, in several classes. Here are the basics:
Hydrangea macrophylla: Prune in late summer, as soon as the flowers fade, but never after September. Remove weaker stems from the base of the plant, being careful to retain several stems of old wood, which will produce buds for next year's flowers. You can prune now, too, but it will cost you flowers this year.
Hydrangea arborescens Grandiflora: Cut to the ground in late winter/early spring. If it survived the winter nicely, however, and you'd like it to grow better, do a light selective pruning, cutting branches at varying heights.
Hydrangea paniculata Grandiflora (Peegee): Simply remove spent flowers; thin or cut back last year's growth in late winter/early spring.
Hydrangea quercifolia (Oak-leaf hydrangea): Remove dead wood at the base of the plant in early spring.
Hydrangea anomala petiolaris (climbing hydrangea): Unruly vines can be shortened in summer. Otherwise, pruning is seldom necessary.
The three-cut method
Use this for branches with a diameter of 1 inch or more.
1 Cut the branch halfway through from underneath, a few inches from the trunk.
2 Move your saw a few inches farther out on the branch, away from the trunk, and cut the whole branch off from the top. This eliminates the weight of the branch and prevents tearing.
3 Make the third and final cut just outside the branch-bark ridge, sawing through the entire branch to the outside of the collar. If you were to make this complete cut without having done steps 1 and 2, the weight of the branch would cause it to rip just before separating, and the tree would have a difficult recovery and a larger area through which disease could enter.