By Ron Dieter, Sunnyfield Greenhouse & Gardens

November 25, 1998

In the past few days I have received several inquiries about caring for clematis vines during the winter. Some gardeners ignore their clematis and prune it only after it threatens to tear the gutters off the house. Others carefully prune every couple weeks, guiding young vines carefully over the trellis. The fact is, most clematis will survive either treatment, but the rule books spell out the official pruning method recommended by the experts.

The experts have divided clematis varieties into three groups, based upon when they flower. Each group is pruned a different way. You need to know which variety you have in order to know how to prune it correctly.

Group A includes all the early-flowering clematis. They bloom in April and May from buds produced the previous season. That means they should not be pruned until right after they flower. If you prune them at this time of year, you won’t kill the plant but you will be cutting off next spring’s flowers. It’s fine, however, to prune out dead and broken vines and to trim back a straggler here and there now or anytime. This group includes Clematis montana, C. alpina, and C. macropetala.

Group B includes the large-flowered hybrids that bloom in June from last season’s wood. Don’t prune these back now, but rather trim back any dead and weak stems in March by cutting back the stem tips to the topmost pair of green buds. Old mature vines tend to get bare and ugly at the base over time. When this happens you can either hide the vines legs by planting something in front of it or you can cut the whole thing back to about twenty inches after the flush of blooms in June is over. Then the vine will either die (not likely if well established) or rejuvenate itself quickly. C. ‘Nelly Moser’ and C. ‘Henryi’ are representatives of this group.

Group C is the late flowering clematis and, as you might expect, they bloom on the new season’s growth. Chances are, if you have a clematis that has been in your landscape for a long time, it belongs to this group. These vines should be cut back to about 15 or 20 inches above the ground every March. Some gardeners cut them back now and that’s fine. Others don’t even own a pruning shears and their vines do just fine. The point is that this is the easiest group to handle because they do fine in spite of how they are cared for. The common and popular C. x jackmanii with its large purple flowers, C. viticella, which bloom most of the summer, and C. ternifolia (paniculata, maximowicziana), the sweet autumn clematis all belong to this group.

Don’t be afraid to prune established clematis vines. You’re not going to kill them with a pruning shears and I’ve never seen a clematis that couldn’t benefit from a snip or two. The worst that will happen is that you will lose some of the flowers for one season.

Before winter sets in, make sure the soil around the base of the vines is well mulched. Check the trellis to be sure it is secure. A loose trellis could cause the base of the vines to become injured and broken in winter winds. And if the wooly worms are right, loose trellises may end up several blocks away by next spring.