It's prime time for winter pruning — but beware of overdoing it

February looks to be seasonably cold again after a period of mildness that kept much of January frost-free. This in turn caused certain plants to stir. My first snowdrop appeared Jan. 14 and was later joined by a few others. Many of my daffodils and crocuses are up a few inches.

The mild winter — following the deep freezes of December — has been a boon to other plants as well, particularly the shrubs and small trees that bloom in winter, as the weather allows. One of the showiest is the winter jasmine, with its bright yellow blooms atop mounded stems. Another is the leatherleaf mahonia, a formidable hollylike shrub whose prickly foliage is leavened by sprays of golden blossoms, small and cupped and fragrant.

Despite its name, the autumn-flowering cherry tree trudges through the winter, progressively but cautiously offering its pink blossoms to a cold world. Instead of being cheered by this bravura, many folks think this is the cherry blossom of early April and the sky must be falling. Maybe it is — last year was the hottest on record — but the temperature swings of winter in these parts have always seemed to define the season for me. What we are witnessing are the natural cycles of these plants, nudged along by the balminess and then checked by the returning chill. The best a gardener can hope for is that the warmth didn't induce too much tender growth and that weather stays cold long enough to keep buds protected until it's safe for them to open.

This is the season for pruning shrubs and small trees, when they are dormant and the absence of leaves gives a clear view of what needs to be done. Fine pruning is like grooming a show dog — it makes for a fine beast — though it is done for the benefit of the plant, not the viewer. If you prune to make a woody plant conform to an idea of shape or structure, rather than help its biological needs, the results can be disastrous. In a month or so, “landscapers” will be going around dismembering crape myrtles, for payment.

Competent pruning, on the other hand, lifts both the shrub (or small tree) and the spirits of the gardener. The more neglected a specimen, the more it can be improved, though the rule of thumb is not to remove more than one-third of its mass annually for fear of traumatizing the plant. This means taking the long view. When I see an old, neglected and congested weeping Japanese maple, I know I could spend hours, days, bringing back its sculptural qualities but incrementally over several winters.

There are exceptions to this conservative approach. Every two or three years, I cut back hard — but not quite to the ground, as you want some top growth remaining — my stand of winter jasmine. I know its well-established root system will produce new growth in the spring, even if it looks ragged for a few weeks. Do this in March, after final flowering, but check first to see that birds haven't built nests. I would give the same treatment to forsythia, a shrub with little garden value but useful for forcing indoors in late winter.

January's warm spell encouraged me to tackle a shrub I've been meaning to clean up for the past two years; actually, it's not just a shrub but a stand of bottlebrush buckeye, which has the distinctive leaves, candelabra blooms and chestnutlike fruit of buckeye tree species but is a large suckering shrub. I planted three sticks 20 years ago, and they now provide a valuable and handsome screen, 12 feet high and 25 feet across.

The goal in pruning a shrub like this is to achieve a chalice-shaped plant with an open interior to let in air and light. First, I remove branches that are rubbing. The art to this is in imagining what the shrub would look like with either of the two candidates gone. Keep the one that enhances the overall shape.

Next you take out inward-growing branches. On a suckering shrub, you want to prune at least half the erupting suckers but leave the rest as a way of revitalizing the plant.

The key to winter pruning is to take your time and be conservative. If you're not sure you've removed enough, come back to it the next day or next weekend with fresh eyes.

I give extra attention to any young tree planted in the past three years. This is the time to establish a framework of branches that grow outward, don't unduly shade other branches and keep the plant looking handsome. Do yourself a favor and buy a new, sharp pruning saw; it will halve the amount of effort.

Now is the time too to prune back the roses, whose little, red buds are close to bursting into life. Leave five or so canes, trimmed to about 18 inches. The same principles apply: Get there by removing stems that are diseased, weak, growing inward or rubbing. Today's landscape roses don't need the pruning finesse of hybrid teas. Long-handled lopping shears will work and have the added value of keeping your body away from the thorns. But don't forget the sturdy gloves.

My Diane witch hazel has a habit of retaining its dead leaves, which veil the now fully extended red blooms. Removing the leaves is a perfect “side job” while you're out pruning stuff. Some leaves will yield to a measured pull; more stubborn ones must be cut off with the pruners. This takes care to avoid slicing through the blossoms.

The other thing the winter pruner has to watch is the placement of feet. Stay away from the shoots of spring bulbs now that they have begun their march to glory.