Pruning Clematis How do I prune my clematis? When your clematis blooms will tell you how to prune it. Clematis are generally grouped into one of three categories based on when they bloom. If you are unsure which group your clematis falls into, let it grow unpruned for a couple of years and note when it flowers. Young clematis and clematis that are not rampant growers do not need a great deal of pruning. Pruning will eliminate some of the dead wood that accumulates in old clematis.
Group I clematis Flower early in the season, before the 4th of July. As with most shrubs that bloom early, they flower on growth made the previous summer or ‘old wood.’ There are a couple of ways of pruning these clematis. In spring, when you can see the buds beginning to swell, prune away dead or damaged growth working from the top down to a pair of nice fat buds highest on the vines. Or you can wait and prune this type of clematis right after it blooms. If the clematis is old and you want to get rid of a mess of dead stems, pruning more severely after blooming in early summer will give the plant time to put out new stems. The new growth pushed out after pruning will be the stems the clematis will flower on the next year.
Group II clematis Flower more or less throughout the season. There may be a flurry of flowers early in the season and then more flowers later in the summer. The early flowers are from old wood while the later flowers are from new wood. You do not need to prune these plants at all unless they become a tangle of old growth. If that happens, you can prune early in the season and sacrifice the early flowers or wait until the first flush of bloom is finished and prune as you would the Group I clematis. Summer pruning will sacrifice later flowers but will give you lots of new growth for early bloom the next year. If you have the patience for it, you can prune lightly and disentangle dead wood in spring before new growth begins.
Group III clematis bloom on ‘new wood’ or stems that have grown that same year. This group is the easiest to prune. These clematis bloom late in the season – summer through autumn. Cut the stems back to strong buds about a foot or so from the ground. ‘Sweet Autumn’ Clematis (Clematis terniflora), ‘Duchess of Albany’ (C. texensis), and ‘Polish Spirit’ are examples of clematis in this group. If you want to read more on pruning clematis, Fine Gardening has a detailed article by Lee Reich. Click on this link.