When should I prune evergreen shrubs?

Deciduous shrubs are pruned in winter dormancy or after flowering. Evergreens are not fully dormant, they carry their leaves through the cold, and they respond differently, so the general shrub rules only partly apply. The most important difference is the one that catches people out with hedging: many evergreens carry no dormant buds in old bare wood, and a cut into it never grows back.

Step by step

1. Use mid to late spring as the default window.April into May in most of the UK, once the risk of hard frost has passed and as the plant starts into growth. Cuts made then callus quickly, and the new growth has the whole season to harden before winter.
2. Prune flowering evergreens after they flower instead.Camellias, rhododendrons, evergreen azaleas, choisya, escallonia and viburnum tinus all set the following year's buds after flowering, so they are cut as soon as the flowers finish. The flowering rule beats the seasonal one.
3. Never prune evergreens hard in autumn.The plant responds by pushing soft new growth that has no time to harden, and the first hard frost kills it. On an evergreen that damage is visible all winter.
4. Establish whether the plant will reshoot from bare wood before you cut into it.This is the critical question. Yew, box, holly, laurel, privet, escallonia and photinia will break from old wood. Most conifers — leylandii, thuja, juniper, chamaecyparis, pine, spruce — will not, and a cut into brown wood leaves a permanent dead patch.
5. Work within the green on conifers.Trim only into growth that still carries foliage. Once you have cut back to bare brown stems there is no recovery, which is why an overgrown leylandii cannot be reduced in width and why regular light trimming is the only workable maintenance.
6. Prune broadleaf evergreens by thinning rather than shearing where you can.Taking whole branches out from inside a laurel, a holly or a viburnum keeps its natural shape and lets light in. Shearing produces a dense outer shell with dead twiggy growth behind it.
7. Cut large-leaved evergreens with secateurs, not a hedge trimmer.A trimmer slices laurel and other large leaves in half, and the cut leaves turn brown and stay on the plant for months. Secateurs are slower and the plant looks considerably better.
8. Renovate hard only in spring, and only on a plant that will take it.Yew, box, holly, laurel, privet and photinia tolerate hard renovation in mid spring. Do one side or one third at a time on a large plant, feed and mulch afterwards, and water through the following summer.
9. Check for nesting birds before any substantial cut between March and August.Evergreens provide the densest nesting cover in most gardens, and disturbing an active nest is an offence. Look and listen carefully, and postpone if there is any doubt.

Tips

• Yew is the one conifer that regenerates reliably from old bare wood, which is why ancient yew hedges can be cut right back to the trunk and recover. Do one face one year and the other a year or two later.
• Frost damage on an evergreen looks alarming in March and often recovers. Wait until growth restarts in May before cutting anything out — you will usually be removing less than you thought.
• Variegated evergreens frequently throw plain green reverted shoots. Remove those as soon as they appear, cutting back into variegated growth, because reverted shoots are more vigorous and eventually take over.
• Silver and grey-leaved evergreens are usually Mediterranean subshrubs and follow the subshrub rule instead: never cut into bare old wood.

Common mistakes

• Cutting a conifer back into brown wood to reduce its size — Most conifers have no dormant buds in old wood and the cut area stays dead permanently. Only yew reliably breaks from bare wood.
• Pruning evergreens in autumn — The soft regrowth is killed by the first frosts and the damage is visible right through the winter.
• Trimming laurel with a hedge trimmer — The cut leaves brown off and hang on the plant for months. Secateurs give a far better result on any large-leaved evergreen.
• Shearing the outside of a broadleaf evergreen year after year — You build a green shell over a dead interior, which cannot be recovered without a hard renovation.

Questions people ask