A crew-cut for the wistaria: Pruning is for your benefit, not the plant's. Be firm, advises Anna Pavord

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The Independent Online
'NEEDS a good haircut,' an old neighbour of ours used to growl, if ever I took him to see a shrub in the garden of which I was particularly proud. For obvious reasons, these little forays soon came to an end. Shrubs were not his thing, anyway. All ground not growing food was wasted as far as he was concerned, and the few shrubs in his own garden were all given short back and sides to keep them from shading the potatoes and the beans. Forsythia, lilac, flowering currant, guelder-rose were all reduced to the same bristling outline.

He may have had a point about the food plants, but it was no wonder he had not grown to love his shrubs. Barbered as they were, they never had a chance to show him what they could do. You need to understand something about a plant's way of life before you can start to understand pruning.

Pruning is something we do because we want to enhance a plant's performance by way of flower, fruit or foliage. We do it for our benefit rather than the plant's. So if it flowers and fruits on new wood rather than old, cutting off its new growth at regular intervals each year is not going to help its performance.

Conversely, some plants, such as vine and wistaria, get so carried away with producing new growth, they need to be brought up short. 'Hey]' you say firmly, as you flash in with your secateurs, 'You are here to make grapes (or bundles of flowers, as the case may be), not to muck about with all this leafing.'

By cutting back vines now, you can persuade them to put maximum effort into fattening up bunches of grapes. The laterals - the side branches of the vine - will already be bearing tiny bunches. Cut back these laterals, leaving just two leaves beyond each bunch. Where there are laterals with no flowers or fruit, cut them back to five or six leaves each.

You need to tackle wistaria equally firmly. A determined slaughter of the waving new shoots now will concentrate their minds wonderfully on a display of flowers next May. Wistaria pruning is a half-and-half business: half now, half in February. Just shorten excess growth at this stage by about half, and finish the job in February, when you should leave only two or three buds on each side shoot.

Wall shrubs are the ones that cry out most urgently for attention now, especially where they are lurching out from the wall and shading borders below. Ceanothus can be a bully in this respect. Wall- trained specimens are generally the less hardy evergreen types such as 'Trewithen Blue', which flower in late spring.

With wall shrubs, training and tying in is as important as pruning. If a relatively tender shrub such as the ceanothus sticks its nose out too far from the shelter of its wall, it is far more likely to suffer damage from wind and frost. And once you have established a tied- in framework, it is much clearer what to prune and what to leave alone.

Tie in the main stem vertically and spread the side branches out as close to the horizontal as you can. Prune out any shoots that grow out of the back of this framework and point straight at the wall. This can be done at any time of year.

General pruning is best done immediately after the ceanothus has finished flowering. Or now, if you did not do it then. Trim back the forward pointing growths (often called breastwood), which are the ones most likely to become a nuisance. Leave 4-6in on each trimmed shoot. Other side shoots can be tied in or cut back, depending on whether you are encouraging or discouraging spread.

Autumn-flowering ceanothus, generally the deciduous types (though there are evergreen varieties such as 'Autumnal Blue') should, of course, not be pruned now, as you would be snipping off the display still to come. These are less often grown as wall shrubs, and if space is unlimited, you can give them their heads. If not, thin out the wood in April, cutting the previous year's growth back to within 3in or so of the older wood.

Japonica needs regular pruning when it is grown against a wall, although a free-standing bush can mostly be left to its own devices. The best time to prune a wall- trained japonica is just after it has finished flowering. Or now, if you have forgotten. Cut back any forward-facing shoots that you do not want to tie in, reducing them to two or three buds.

The idea is to encourage it to form more flower buds than it might if left alone. It also helps, especially when you are short of space, to have it flattened against the wall, like the cat in a Tom and Jerry cartoon. If this seems too imprecise, get hold of a manual.

Two were published this spring, peppered with diagrams of well- behaved shrubs that throw their branches out at regular intervals and never do anything they shouldn't. Unfortunately, gardeners are usually presented with loutish specimens that refuse to conform to type. The Essential Pruning Companion, by Professor John Malins (David and Charles pounds 20) is the more entertaining of the two books. Trees, shrubs, climbers, conifers, hedges, topiary, roses and fruit are all covered.

Pyracantha also needs attention if it is grown against a wall, although you can leave it alone if not. As with japonica, you want to limit the amount of growth that lurches forward, to the detriment of plants beneath. Pyracanthas are such hardy beasts that you can snip away at any time without putting them off their stride.

Trim back forward- facing shoots severely and tie in any other growth that you want to keep. Train shoots now, before they become too woody. If caught young, they are extremely biddable.

Rose pruning is generally seen as a winter job, but ramblers need pruning in summer. They are best grown not on walls but on an open trellis or up a tree, where the wind can blow through them. On a wall, they are more prone to mildew. The aim here is to encourage a fresh supply of new wood to break from the bottom of the rose, or as low down as possible. These are the stems that will flower next summer.

Take out one or two of the old growths entirely. I generally match the amount I take out with the number of new growths already showing. If there are no new growths, take out an old one anyway and trim back the rest of the stems to fresh shoots.

If the rose is in a tree you will be more restricted in what you can reach. At the National Trust's garden at Hidcote, Gloucestershire, where immense roses drip out of hollies and yews, the gardeners trim the hanging flowered stems back to a point where a vigorous new side shoot is taking off.

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