Time Your Cuts Around the Plant's Own Clock

Shrubs do not all want the same treatment, and the most common mistake in British gardens is reaching for the secateurs at the wrong moment. The guiding principle is simple: prune when the plant can afford to lose the wood, and when it has enough growing season left to replace it. A shrub that flowers on last year's growth — forsythia, philadelphus, weigela, ribes — should be cut straight after flowering in late spring or early summer, so the new shoots it makes have the rest of the season to ripen and carry next year's buds. Cut those in winter and you remove the very wood that would have flowered.

Shrubs that flower on the current season's growth — buddleja davidii, hydrangea paniculata, caryopteris, ceratostigma and most spiraeas — are happy with late winter or early spring pruning, cut back before growth restarts. It is tempting to tidy in autumn, but autumn cuts push soft new growth that has no time to harden before the frosts, leaving an open wound through the wettest months of the year. Where you can, wait for late winter.

Start With the Three Ds

Before you shape anything, before you think about next year's flowers, walk around the shrub with a pair of sharp secateurs and take out what the plant is already trying to shed. Dead, damaged and diseased wood comes out first, always.

• Dead wood — test by bending. Live wood flexes, dead wood snaps. If you are unsure, scrape a sliver of bark with a fingernail and look for green beneath.
• Damaged wood — storm-broken or rubbed branches, stubs left by clumsy cuts, and stems that cross and chafe against one another.
• Diseased wood — cut back to clean, healthy tissue, and wipe your blades between plants with methylated spirit or a diluted garden disinfectant.

Only once the shrub is reduced to a clean, living framework should you think about shaping it. On many shrubs this first pass is all that is needed, and you can stop there with a clear conscience.

Read the Wood Before You Cut It

The buds tell you everything. On young, vigorous stems you will see buds sitting along the length of the shoot, ready to break if you cut above them. Further down, on older, thicker, greyer wood, those buds are often dormant or gone altogether. The bark is bare, and a cut there may die back or simply heal over without ever producing a shoot.

This is the difference between thinning and butchery. Aim to cut back to a healthy outward-facing bud on wood young enough to respond, at a slight angle sloping away from the bud and roughly 5mm above it. Too close and the bud dries out; too far and you leave a stub that dies back and invites rot. If you are shortening a branch to a side shoot, cut just above the join rather than leaving a length of bare stem behind.

When Hard Renovation Is Safe — and When It Is Not

Some shrubs resent being cut into old wood and will respond with little more than a stump. Others are remarkably forgiving and will throw up strong new growth from the base or from old limbs. Knowing which group you are dealing with saves years of disappointment.

• Regenerates well from old wood: buddleja davidii, cornus, cotinus, forsythia, philadelphus, weigela, deutzia, ribes, salix, hydrangea paniculata and most spiraeas.
• Take renovation gently, or not at all: lavender, rosemary, cistus, daphne, magnolia, rhododendron and azalea, ceanothus, hebe, skimmia, and most conifers, which will not reshoot from bare wood.

With the cautious group, work in stages: take out a third of the oldest stems each year, always cutting back to a younger shoot or down to the base, and accept a looser shape in the meantime. Never shear a lavender or rosemary into the leafless old centre — it will not come back, and you will be left with a woody gap you cannot hide.

Sharp Tools, Clean Cuts, Calm Aftercare

Blunt blades bruise bark and crush the cambium, leaving a ragged wound that heals slowly. Use bypass secateurs for stems up to finger thickness, loppers for anything up to about 3cm, and a pruning saw for thicker limbs. Do not force the secateurs and twist. On a thicker branch, make an undercut first, then cut from above slightly further out, and finally remove the stub. The limb falls cleanly rather than tearing a strip of bark from the trunk.

After pruning, a light mulch of garden compost or well-rotted manure around — but not touching — the base helps the shrub recover. Resist a heavy nitrogen feed that would push soft regrowth late in the season; a balanced feed in spring is plenty. Water new plantings in dry spells, and then leave the plant alone to do its own work.

Finally, expect a response rather than perfection. A shrub you have pruned well often looks a little thin for a fortnight and then bursts. Look at it again in six weeks, thin out any crowding shoots, and let the plant guide the next cut.