Why Winter Suits the Saw and the Secateurs

For most deciduous shrubs, the quiet weeks between leaf fall and bud burst are the kindest time to get the pruning done. With the leaves gone you can actually see what you are dealing with — the framework of stems, the awkward crossing branches, the dead wood that has been quietly hiding all summer. The plant is dormant, so it is not wasting energy repairing damage, and it will throw its reserves into new growth when spring arrives.

There are limits. Avoid cutting in hard frost, when frozen wood can shatter and wounds seal poorly. Steer clear of the few shrubs that bleed heavily if pruned in winter — maples, birches and walnuts among them — and leave those until late summer or autumn instead. For everything else, a dry, mild spell between December and early March is ideal.

Begin with the Three Ds: Dead, Damaged and Crossing

Before you think about shape or size, clear the clutter. Work through the shrub methodically and remove, in this order:

• Dead wood — brown, brittle and hollow-sounding. Snap a thin piece or scrape the bark with a fingernail; if there is no green beneath, it is dead. Cut back to healthy wood, following the stem down until you find it.
• Damaged branches — snapped, split or wind-rocked stems, which are open invitations to disease.
• Crossing and rubbing branches — these chafe against one another, creating wounds that never heal cleanly. Take out the weaker or more awkwardly placed of the pair and keep the better one.

Cut cleanly and avoid leaving long stubs, which die back and provide an entry point for rot. Once this first pass is done, the shrub usually looks far less daunting, and you can judge what genuinely needs thinning.

Then Thin Crowded Growth for Air and Light

Dense, congested growth is where trouble starts: poor airflow around the centre of a shrub encourages powdery mildew, grey mould and a host of other fungal problems. Thinning lets light and air reach the middle, ripens the wood and keeps the plant vigorous.

The trick is to thin rather than trim. Cutting all over the outer surface with secateurs simply creates a bristly shell of short shoots and a still-congested centre. Instead, take out whole stems at the base. On multi-stemmed shrubs — cornus, salix, physocarpus, cotinus, sambucus and the like — remove up to a quarter to a third of the oldest, thickest stems right down to ground level each year. Over three years you renew the entire shrub without ever giving it a shock.

For a shrub that has simply outgrown its space, shorten it gradually. Removing more than a third of the top growth in one go invites a thicket of weak regrowth. Spread the reduction over two or three winters and the plant will keep its shape while it comes back under control.

Hold Off on Spring Flowering Shrubs

This is the rule that catches most gardeners out. Shrubs that flower before midsummer generally do so on growth made the previous year, which means the flower buds are already sitting on the stems you are about to cut. Prune them now and you prune away the display.

Leave these well alone until immediately after they bloom: forsythia, flowering currant, Japanese quince, lilac, kerria, deutzia, philadelphus and weigela. A simple guide is to prune a shrub straight after it has finished flowering if it blooms before midsummer, and in late winter or early spring if it flowers from midsummer onwards on new wood.

Hydrangeas need a little more thought. Mophead and lacecap types flower on old wood, so tidy them lightly in spring, removing only the old flowerheads and any dieback. The paniculate and smooth hydrangeas flower on new growth and can be cut back hard in early spring without losing a thing.

Cuts, Tools and a Little Aftercare

Sharp tools make clean cuts, and clean cuts heal. Bypass secateurs for stems up to about a centimetre, loppers for anything thicker, and a pruning saw for genuinely woody limbs. A blunt blade crushes tissue and leaves a ragged wound that takes far longer to seal.

Where you are heading a stem in a particular direction, cut just above an outward-facing bud, angling the blade slightly away from it so water runs off. Where you are removing a stem entirely, cut as close to the branch collar or ground level as you can without gouging the parent stem — no stubs.

If you suspect disease, wipe your blades between shrubs with methylated spirits. Afterwards, clear the prunings away rather than leaving them on the border, and mulch around the plant with a five to eight centimetre layer of garden compost or well-rotted manure, keeping it clear of the stems themselves. There is no need to feed heavily in winter; the mulch and the spring warmth will do the work.

Finally, remember that shrubs are forgiving. If you are unsure, take less rather than more, stand back, and look again. You can always remove another stem next winter — but you cannot put one back.