Exercising your secateurs on messy shrubs may feel good but can often be to the detriment of future growth. Christopher Lloyd provides some expert advice on when and how to prune

There is pruning that we can do now, as soon as the leaves are off and we can see a shrub's requirements clearly. But there is also a lot that is best left till spring and more still that amounts to a hack-back, rather than pruning. Hacking back may give immediate satisfaction to the hacker but it may be doing a lot of unnecessary damage to the shrub.

Take the vigorous Clematis montana, for instance. It has got all over everything. In the interests of the autumn tidy-up, it is tempting to give it a short back and sides, even if only to show who is master here. What has not been appreciated is that every one of those long strands that has been removed, contained the embryo of upwards of a hundred blooms for next May, and they have all been sacrificed. The solution is to leave all the spring flowerers alone for now, and to prune them as necessary immediately after flowering.

It is the same with forsythia, which is all too often seen as an ugly ball of chopped-back shoots. Often the root of the problem is that, as a vigorous shrub, it was not given enough space in which to develop in a dignified manner in the first instance. One way to manage a forsythia is to remove its oldest branches, right into the centre of the bush, just before it is about to flower and to bring them indoors to force gently into bloom there. Early February is the best time to do this; certainly not now.

The shrubs to manage after leaf fall are hardy ones that it is a good plan to rejuvenate on a regular basis, such as philadelphus, deutzia, weigela, kolkwitzia (beauty bush) and kerria. Remove their flowered branches, easily identified by their twigginess, and leave those long, unbranched shoots that it made this year and will flower for you next. DO NOT tip these. Leave them full length.

The branches you remove should be cut either at ground level or, if a strong young branch arises from an old one, just above this branch. In this way you open up the bush, letting light into its centre and thereby encouraging it to make more young growths in its next flowering season. You also reduce its overall bulk. An old, unpruned bush will take up valuable space but the whole of its centre will be useless, contributing nothing and simply accumulating dead or hopelessly weak growth.

If you inherit such a specimen and contemplate it dejectedly, wondering where on earth to start, since there seems to be no strong young growth anywhere, you must be drastic, either restoring it to youthful productivity over a couple of seasons, or by getting rid of it altogether and starting again (often the best policy and you can buy yourself what you know to be a good variety).

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