Why timing matters more than technique

Pruning fills many gardeners with a wobble of doubt. We stand there, secateurs in hand, wondering whether we are about to help the shrub or ruin it. The good news is that for most garden shrubs, timing matters far more than the angle of the cut. Get it right and the plant forgives almost anything. Get it wrong and you can spend a year waiting for flowers that never appear.

The rule hangs on one question: when does the shrub flower? Once you know that, the calendar almost writes itself.

The one question that decides everything

Shrubs fall into two camps. Spring-flowering shrubs bloom on growth made the previous year, from late winter to roughly the end of June. Summer-flowering shrubs bloom on growth made in the current season, from roughly July onwards.

That difference dictates when to prune. Spring-flowering types are pruned after they bloom, so the plant can grow next year's flowering wood. Summer-flowering types are pruned in early spring, before that year's growth begins, because hard cutting encourages vigorous, floriferous new shoots.

Prune a spring-flowering shrub in winter and you cut off the flower buds already sitting there. Prune a summer-flowering shrub in autumn and you leave it exposed to cold and waste the energy stored in its stems.

Spring-flowering shrubs: prune straight after bloom

This group includes forsythia, lilac, philadelphus (mock orange), weigela, deutzia, kerria, flowering currant and early spiraeas. They light up the garden early, then spend the rest of the year building the stems that will flower next spring.

Prune within a few weeks of the flowers fading — by mid-July at the latest. Don't put it off until autumn. A practical approach:

• Remove the oldest, darkest stems at ground level to encourage fresh growth from the base.
• Cut flowered shoots back to a strong young shoot lower down, not to a random point mid-stem.
• Thin crowded growth in the centre so light and air reach the plant.
• Step back every few cuts and check the shape; aim for an open, natural outline, not a tight ball.

Lilacs are a good example. Cut them hard in winter and you lose most of the flowers, but a light tidy after blooming, plus removing a few old stems each year, keeps them flowering generously for decades.

Summer-flowering shrubs: prune in early spring

This group rewards boldness. Buddleja davidii, caryopteris, perovskia (Russian sage), hydrangea paniculata, hardy fuchsia and the colourful stems of cornus and salix all flower on new growth made in the same year.

Prune in March or early April, once the worst frost has passed but before growth really starts. The technique is usually to cut back hard:

• Buddleja can be cut to 30–60cm from the ground, leaving a low framework of healthy stems.
• Hydrangea paniculata and caryopteris can be cut back to a framework of two or three buds per stem.
• Hardy fuchsias are best cut back to a low permanent framework in spring, once new shoots appear at the base.

It can feel brutal, especially the first time. But this is what keeps these shrubs young, compact and smothered in flowers rather than tall, woody and bare at the base.

Always start with the three Ds

Whatever the timing, begin every pruning session the same way. Remove the three Ds: dead, damaged and diseased wood, plus any branches crossing and rubbing each other. This is not just tidying — it is plant health.

• Dead wood is brown and brittle when scratched; cut back to clean, living tissue.
• Damaged wood — snapped, split or wind-rocked stems — should be cut to a healthy side shoot or bud.
• Diseased wood should be cut well below the affected area, and your secateurs cleaned afterwards.
• Crossing branches create wounds that let disease in; remove the weaker of the two.

Make your cut just above an outward-facing bud or side shoot, at a slight angle, and don't leave long stubs. Sharp tools make clean cuts; blunt ones crush stems and invite problems. Bypass secateurs, loppers for thicker stems and a pruning saw for anything really woody will cover almost every job in a British garden.

Evergreens and the awkward exceptions

Evergreen shrubs such as Viburnum tinus, choisya and photinia are best pruned in late spring or early summer, while in active growth. They respond well to light trimming, but many will not regrow from old, bare wood, so never cut back harder than you need to. Conifers are stricter still: trim only the current season's growth, ideally in late spring, and avoid cutting into the brown, leafless centre.

Some plants refuse to fit either camp. Hydrangea macrophylla (mopheads and lacecaps) is the classic awkward one: in mild coastal areas you can prune after flowering, but in colder gardens leave the old flower heads on over winter, then prune in March, cutting back to a pair of healthy buds. Lavender should be trimmed lightly straight after flowering, never into old, woody stems. Wisteria is a law unto itself, with its summer and winter routine.

When in doubt, light pruning almost always beats hard pruning. If unsure about a shrub, leave it for a season and watch when it flowers. The plant will tell you what it wants. And if you do make a mistake, don't worry — most shrubs are far more resilient than we give them credit for. A year without flowers is a small price for learning the rhythm of your garden.