Pruning Your Clematis

Clematis pruning is something that often worries people, maybe because the plant label refers to a pruning Group, or Code, and this creates uncertainty. It is, however, quite logical and straightforward. Group 1 are the first to flower, early in the year. Group 2 are next to flower in the summer, and Group 3 are the last to flower later in the summer.

Group 1 clematis include the widely grown C montana, C alpina and C macropetala, as well as the evergreen winter flowering species such as C cirrhosa and C armandii. All of these flower on stems which have grown the previous year. They do not need regular pruning, but wayward stems can be removed as the flowers go over. C montana is very vigorous and sometimes gets too big for its space, in which case it can be cut hard back, even to ground level, just after flowering, but this should not be done on a regular basis.

Group 2 clematis start to flower in late spring or early summer, and have a long season, especially if well fed and cared for. Most of the showy, large flowered and brightly coloured hybrid clematis are group 2, for example General Sikorski, Nelly Moser, Guernsey Cream and Piilu. The flowers come from growth made the previous year, so they are pruned in late winter or early spring (February is ideal) by cutting back the old growth to above a pair of strong buds. The cuts will be at different heights on the stems which gives a natural and staggered arrangement of flowers on the plant. These clematis will often rally themselves to have a second flush of flowers later in the summer, this time on stems grown in the current season; trimming off spent flower stems from the first flush will encourage this.

Group 3 clematis are the later flowering varieties including named varieties of C viticella, C tangutica, C orientalis and C texensis. These all flower on growth made in the current year, so they are cut hard back in the spring to a healthy bud at about knee height. It is tempting to leave all the higher growth which may already be showing signs of healthy new growth, but if left unpruned all the flowering will be way up on the plant, out of sight. As for group 2, late winter or early spring is the right time to do this, as the buds are beginning to swell.

We are commonly asked what to do with an unidentified clematis. The old saying is “if it flowers before June, do not prune”. The best plan is to wait and see when it flowers, and if possible make a note of when it starts, and take a picture. This information should be enough to work out which type of clematis it is, and if you bring us the photo we may be able to help with the variety. Finally, it is a good idea to feed your clematis at the same time as pruning. A high potassium fertiliser (such as rose or tomato food) applied around the base of the plant will assist flowering.

Another group 3 Clematis, 'Sweet Summer Love', showing vigorous top growth from last year which has been removed.