Pruning Clematis

by Alan Titchmarsh

Ever since the great clematis craze started – oh, it must be 20 years ago now – these showy climbers have never been out of fashion with gardeners. Each year a few new varieties come onto the market, and they are always stunners. Somehow, we keep shoe-horning a few more  into our gardens, somewhere.

But there comes a point when the more elderly specimens start to look a tad threadbare, twiggy, and straggly. Old clematis go on almost forever, but my goodness they benefit from an occasional facelift, and the one thing most people never think of doing is pruning them.

It can all seem quite complicated, since clematis fall into several camps when it comes to pruning. The easiest way to sort them all out is to hang on to the labels that come with the plants when you first buy them. By filing those safely away, you always have the pruning instructions for each variety on hand.

But do tie a name tag to the plant itself; then even if you lose the original label, you can always look up the precise instructions in a reference book. But even when you have a hotchpotch of varieties with no names, all is not lost, if you can remember what their flowers look like and roughly when they bloom.

You can identify the large-flowered hybrids by their huge saucer-shaped flowers 4-6in across. They are by far the most popular kind of clematis. Now is the moment to prune these, now that you can see where those silky shoots are beginning to sprout from.

These large-flowered varieties fall into two sub-groups, but bear with me. The sort that flower once, in a single long continuous flush from mid June to early autumn, need hard pruning; cut those down to about 4-6 inches above ground level any time over the next fortnight. (Why? It’s because these varieties flower at the tips of their shoots, so unless you hack them down hard every year the flowers will all be up high with lots of bare-ish stems below).

The sort that flower twice each summer, early and late, carry their first batch of flowers on short sideshoots from last year’s growth, so they only want pruning lightly – just trim off any dead bits and cut their stems back to strong buds.

Small-flowered hybrids such as Clematis viticella have blooms the same shape as the large-flowered hybrids, but only 1-3 in wide, and they flower once, for a couple of months in late summer. Prune these by cutting them right back to within 6in of soil level.

Other kinds of clematis don’t need regular pruning, but as they get on in years and start looking scruffy you can give them a haircut to freshen them up. Spring flowering clematis such as C. alpina and C. macropetala just need cutting back lightly after flowering, to keep them tidy.

Clematis montana varieties can get quite big but if you cut them back slightly straight after flowering you shouldn’t lose out on the following year’s show. If they’ve grow far too big and tatty so you have to take more drastic action, chop them back to a foot or two from the ground, and don’t be surprised if they take a year off before they start flowering again.

It’s worth the hassle; a snip in time saves a frightful mess – not to mention the price of starting again with a new set of clematis.