The clematis, a member of the buttercup family, gets its name from the Greek word for vine, and includes around 250 species and many hybrids. Most clematis plants will be deciduous climbing types, but some can be evergreen. Flowers and foliage differ greatly between the various species. When these plants need pruning depends on when they bloom. Proper pruning techniques should always be used to ensure that no damage occurs.
Clematis vines that bloom in spring produce flowers only on wood from the previous year’s growth. These plants profit best from pruning immediately after they finish flowering. New growth will grow back, but some plants, such as C. Montana, have a hard time resprouting. These plants should be pruned only lightly.
Fine Gardening says that repeat bloomers will bloom in spring on old growth and then again in the late summer on new growth. Pruning these plants requires more care than other types of clematis vines. Several different pruning styles can be used to control growth and shape.
The first approach requires light trimming to thin out the plant. This should be done in late winter or early spring before growth begins. The second light trim comes after the vine finishes flowering in late or early summer.
Another option for pruning means performing heavy pruning every other year. The plant should be cut back by half at each heavy pruning. The last approach requires pruning the vine completely away to the ground just before the growing season. This should be done only every several years. Both of these methods need little to no pruning in between heavy trims.
Summer- and fall-blooming clematis vines produce flowers only on new growth. These vines will be the easiest to prune. According to Ohio State University, these vines need new growth for flowers to form. Prune the plant back just before or just as new growth begins. Stems can be completely cut back to several feet from the ground or to the preferred height. Some clematis vines, such as C. orientalis, bloom slightly earlier, and blooming will last longer into the season if the pruning was less severe.
Along with knowing which type of clematis vine you have, knowing proper pruning techniques will help the plant stay healthy. Before pruning, develop a plan for how the plant should look. Prune away dead or diseased stems first and then selectively remove other stems. Make sure all tools have sharp edges and create clean, smooth cuts.