You've got to be cruel to be kind

This week: pruning
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The Independent Online
Plants present many of the same characteristics as children. An intense period of bringing them on, worrying about the right food and so on, is followed by an equally intense period of trying to hold them back. But gardeners do have one enormous advantage over parents: there is no equivalent to pruning in child care.

It is a mistake, though, to look at secateurs primarily as offensive weapons. Good pruning is a matter of working with, rather than against, a plant. The most important thing, before you make any cuts, is to have clearly in your mind the essential qualities of the plant you are about to attack.

If you have a tall, upright shrub blocking a view in the garden, it is pointless to chop the top off each season in an effort to refashion it as a short, fat shrub. Instead, you must come to terms with the irritating fact that you, or the previous owner of the garden, have planted it in the wrong place. Therefore, it should be moved rather than heavily redesigned. Some tall, upright shrubs - it may be philadelphus or May-flowering kerria - do need regular pruning, but this is not to make them shorter. It is to ensure a plentiful display of fresh new growth that will flower more freely than the old.

Pruning is something we impose on shrubs for our own ends rather than theirs. Shrubs do not die if they are left unpruned, as anyone who has taken over a neglected garden knows only too well. Away from the flashing knife, jasmine just keeps getting bigger. So do pyracantha, forsythia and weigela. Pruning is a useful tool in erecting the delicate barrier against chaos which is at the core of garden-making. A garden is a construct, a reordering of the elements - earth, water, leaves, flowers - that exist untrammelled on the other side of the barrier.

Armed with secateurs and some strong, long-handled loppers, you become a sculptor, releasing the forms suggested by the material to hand. With overgrown shrubs, you have a choice: sculpting or moulding.

The second is the more drastic: cutting the whole thing to the ground and working with the new growths that spring up the following season. This is the best course to take if you want to move a shrub. Unencumbered by top growth, it will be easier to manhandle. It will also find the business of putting down new roots easier if it does not simultaneously have to send food and drink up to the top storey.

This is what I am going to do with an Alba rose that has become ridiculously large and blots out the planting behind it. Once I had become irritated by it, I saw how little it was contributing after its brief, though admittedly heady, season of flowering. It needs a less prominent position. There is still time, before it gets into full growing gear, to cut it down and move it to a new billet.

From this time of the year onwards, gardeners get infected by a kind of fever. We want to get outside and start flailing around, trying to regain possession of the battleground. There is a tendency to snip away at everything in sight, reducing all shrubs, whatever their habit, to barbered buns. Resist the temptation. The garden may be tidy, but by reducing all the shrubs to the same common denominator you will have missed the point of growing them at all.

In the most general terms, shrubs that flower in the first half of the year do so on growth made during the previous year. These can be pruned after flowering. Shrubs that flower in the second half of the year bear the flowers on the new wood they have made in the first half. These are best not pruned straight after flowering, but left until about now.

Pruning kicks a shrub into top growing gear. "Crumbs," it says to itself, "someone's trying to do me in," and it pumps energy into dormant growth buds lying along its stems to replace what it feels it has lost. If you pruned a late summer-flowering buddleia or caryopteris when it had just finished flowering, the resultant tender new growths would coincide fatally with the first frosts. So you leave them until February before pruning.

Buddleia thrives perfectly well without any pruning, as you can see on any railway embankment. But, left unpruned, the bushes get very big. And the trusses of flower coming from old wood are smaller than the ones that are produced on new wood. So, to get the shrub to produce the showiest flowers, you need to persuade it to produce new wood each season.

First, cut out all weak and straggly growths altogether. Then cut back the rest of the growths drastically, leaving just one or two pairs of buds on each branch. Old specimens may become congested after years of this treatment. If a likely looking new shoot springs from below the main framework, take the opportunity to saw away one of the old branches completely.

Rambling roses and rambler types such as 'Albertine' should have been dealt with when they finished flowering last year. The climbers that need attention now are the climbing sorts of hybrid tea roses.

Roses in this group flower on new wood but (unlike ramblers) rarely produce new growths from the base of the plant. You are much more likely to find new shoots growing from old wood higher up the plant. Cut old stems back to the junction with the new growth and tie the new growth in. Cut back the lateral growths (the side branches springing from the main ones) to about six inches. Now and again, it pays to take out a stem completely at ground level, especially when the main framework of a climbing rose has crept higher and higher up its support. This drastic reduction sometimes forces the rose to send out a new shoot from the base. A hefty spring mulch will help, too.

All dogwoods, such as Cornus alba 'Elegantissima', grown for their decorative winter bark, should be cut back hard now. The bark colour is much brighter on new growth than old, so you want as much of it as you can get.

I cheat here and cut just half back each season. That is because I do not want to lose entirely the bulk of the shrub in spring. For the all- or-nothing effect, cut back all growths to within three inches of the ground. Ambivalent gardeners can cut out the dullest-coloured wood and leave the rest. 'Elegantissima' has pretty, variegated foliage, so there is some merit in having this sooner rather than later.

Pruning practicalities

This checklist may help new gardeners to decide which pruning treatment to deal out to common shrubs, and avoid unnecessary haircuts.

No regular pruning; occasional thinning and removal of dead shoots: Abelia, abutilon, acer, camellia, evergreen ceanothus, cistus, cotoneaster, cytisus, elaeagnus, fatsia, genista, hamamelis, hibiscus, hydrangea, magnolia, osmanthus, pyracantha (but can be trimmed to shape if necessary May-July), rhododendron, senecio (cut back flower stems in autumn), skimmia, syringa.

Remove one-third of oldest shoots in spring or after flowering each year, to encourage fresh flowering shoots: Berberis, choisya, cotinus, deutzia, escallonia, forsythia, hydrangea (or leave unpruned), winter jasmine, kerria, philadelphus, phlomis, potentilla, ribes, rosemary, spiraea, symphoricarpos, viburnum (early flowering), weigela

Cut back hard in spring: Buddleia, caryopteris, deciduous ceanothus, ceratostigma, cornus (foliage forms), fuchsia (frost usually does it for you), lavatera, perovskia.