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| Clematis 'Elsa Spath' - Pruning Group 2 |
Carol Klein said: Clematis are usually classified in three groups.
Group 1 includes winter and spring flowering clematis and the simple rule is, leave them alone. 'If it flowers before June, don't prune!'.
Group 2, which include the big, summer-flowering hybrids and all the double flowering clematis, are more complex. They flower on old wood so they must not be cut down to the ground. In the spring you can prune by selecting some really strong buds and chop down just above them. This will encourage the flowers to form and give a good show. The exception to this is the repeat flowerers (they flower again in late summer). In the case of repeat flowerers, when the first flush of flowers has ended you can prune just underneath where they finished flowering and cut back there. This should encourage a second show.
Group 3, like the clematis viticillas, that flower late in summer are straight forward; they always flower on new wood so you 'can be really brutal' and cut them down to about 30cm (12in) from the ground if wished.
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I wrote about pruning clematis in an early article when I wrote about my new (then) additions to the garden: Dr Ruppel and Elsa Spath (Group 2).
Pruning Group 1 Clematis - they can be cut back but pruning is not essential. (see Royal Horticultural advice on pruning group 1 clematis - external link).
Pruning Group 2 Clematis, according to the Royal Horticultural Society (external link):
With clematis group 2, which tend to flower twice in one year, the goal is to keep a framework of older wood yet promote the growth of new shoots in order to have the most flowers throughout the season.
If young plants are left unpruned they can end up with one long stem with flowers on top. This is similar to the problem with unpruned climbing roses.
"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 new plants about 1ft (30cm) above ground level, just above a couple of strong buds. This will encourage the growth of side shoots and more stems which should be tied in eventually.
With older, established plants, they can be pruned in late winter or early spring, say February, by removing any weak or dead growth before buds begin to emerge. Begin at the top, cutting off above the first pair of healthy buds. Avoid pruning hard (too far back) or you'll have less flowers.
When the first flush of flowers has ended, cut back stems to a strong side shoot of above large buds immediately below the flowers. If the clematis is becoming overgrown or top-heavy, some stems can be cut down harder after the first flush of flowers, and the same treatment given to other stems on following years. You are, however, unlikely to get flowers from stems cut back hard until the following year.
There is another choice for overgrown clematis in group 2: Every three or four years you can prune the clematis right down to 1 to 3 ft above ground (30-90cm) at the end of winter, however they will only flower once the next season. Some mid- to late summer flowering clematis can be treated as either pruning group two or pruning group three, as desired.
Pruning Group 3 clematis According to the Royal Horticultural Society, prune group 3 clematis in early spring when they are coming out of dormancy or in late winter when they are dormant.
It's a good idea to prune young, newly planted clematis if they are a little spindly or only have 2 or 3 stems. Cutting back to about 30cm (12in) above ground level, just above a pair of strong buds, will encourage more shoots to develop and thus more flowers.
With established plants, prune back old stems in early spring to about 30cm (12in) above ground level otherwise they will just continue to grow from the previous year's growth and, like climbing roses, will end up with all the flowers at the top and nothing at the bottom!
This group can be left unpruned, however, to clamber over fences, up trees, and pergolas and being more compact is less important.
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List of Group 1 Clematis (Taylors website)
List of Group 2 Clematis (Taylors website)
List of Group 3 Clematis (Taylors website)
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NOTE: Early this year my group 2 clematis, Dr Ruppel, looked unwell. Although it had begun to climb up my garden fence it began to wilt and not because of lack of water. I had no choice but to cut it down to just below where it looked unaffected. It recovered and the upshot is that this particular clematis now has produced a beautiful show of big flowers low down on the fence (on the old wood) and has also produced new, non-flowering growth above (which should flower next year, hopefully).