Cut The Confusion Over Clematis
Don’t let your climbers drive you up the wall. crack
I love the huge flowers of hybrid clematis as they climb up trellis and fencing, or weave their way through less interesting shrubs, wrap themselves around tree trunks and scramble over old walls to create a burst of colour, often in shadier places. They make perfect companions entwined with deliciously scented climbing roses covering arches and pagodas in the romantic garden, or simply climbing up unsightly walls or fences to act as a colourful screen. In fact, different types of clematis can provide you with flowers for most of the year. Yet, clematis are the climbers which cause the most confusion when it comes to pruning because there are three groups of them, and if you prune the wrong type at the wrong time you’ll ruin your chances for blooms this year.
Group 1 clematis, which flower in spring, bloom on stems which grew the previous year and are generally pruned after flowering. They are often rampant growers with large numbers of relatively small flowers - C. macropetala and C. montana are well-known examples, although C. alpina, cirrhosa and amandii also fall into this group. Prune them straight after flowering by clipping the sideshoots back to a few buds of the main framework. They should not be pruned in the winter, or you’ll cut off all the shoots and lose the new season’s flowers.
Now is the time to prune summer-flowering clematis, the Group 2 types, which bloom on stems produced in the current season. They are pruned in late winter or early spring to remove much of last year’s growth. If left unchecked they will produce flowers, but they will tend to be at the end of the plant where you probably won’t be able to see them.
Group 2 clematis include many of the large-flowered hybrids, including the most famous pink striped variety ‘Nelly Moser’, the rich purple ‘The President’ and other popular types including ‘Marie Boisselot’ and ‘Lasurstern’.
The aim with pruning Group 2 clematis is to retain a framework of old wood, and also to stimulate new shoots to maximise flowering throughout the season. Unless the plant already has three or four healthy stems growing from the base, all newly planted clematis should be pruned back hard the first spring after planting.
Cut back to just above a strong pair of leaf buds about 30cm above soil level. This will encourage multiple stems which can be trained into supports to give a good coverage. With established plants, remove dead or weak stems before growth begins, check individual stems from the top down until you reach a pair of healthy buds, and prune just above them, removing the spindly or damaged growth above.
The ones that flower first in early summer, and again in late summer, need a tidy-up rather than a heavy prune. Those which must be pruned now are those which don’t start flowering until June, and keep going until the autumn, as they make vigorous growth and only flower on the very ends of the shoots. They can be cut back to a pair of fresh green buds about 30cm in early spring, and then new growth tied into the supports.
Some mid to late summer flowering clematis can be treated as either Group 2 or Group 3, as desired, including ‘Comtesse de Bouchaud’, ‘Gipsy Queen’ and ‘Hagley Hybrid’.
Group 3 are late summer and autumn-flowering clematis including viticella and texensis and some large-flowered types including ‘Niobe’, ‘Perle d’Azure’ and ‘Ernest Markham’. They flower on both last year’s and the current season’s growth. In the first year, prune them back in late winter or early spring to the lowest pair of healthy-looking buds you can find, which will be about 30-90cm above the ground. This may mean cutting off green, healthy shoots, but the plant will reshoot from the base and be better for it.