How and when do I clip box and topiary?
The two-cut year that keeps box crisp, why you clip on a dull day, the hygiene that reduces blight, and how to bring a shapeless old ball back to a defined shape.
- Difficulty
- intermediate
- Time
- 1 hr 30 min
- Read
- 4 min
- Safety
- caution
Short answer
Clip twice a year — once in late spring or early summer once the first flush of growth has hardened, and again in late summer, finishing by about the end of August so the last growth hardens before frost. Clip on a dull, dry day, sweep up every clipping, and feed and mulch in spring.
Box and other small-leaved evergreens are clipped rather than pruned: you are shearing the outer surface repeatedly to build a dense skin of growth. The technique is straightforward. What has changed in the last two decades is that box blight and box tree caterpillar have made hygiene and vigilance as important as the clipping itself.
Safety
What you'll need
- Sharp topiary shears or single-handed sheep shears
- Powered trimmer for large amounts (optional)
- Sheet or tarpaulin to catch clippings
- Eye protection and gloves
- String line, canes or a template for formal shapes (optional)
- Garden disinfectant for blades
Step by step
- Clip after the first flush of growth has hardened.Late May into June for the first cut, once the soft bright new growth has darkened and firmed. Cutting while it is still soft bruises the leaves and the cut edges brown.
- Make the second cut in late summer and stop by the end of August.This tightens the shape for the winter. Clipping later than about the end of August pushes out soft growth that will not harden before the frosts and will brown off.
- Choose a dull, dry, still day.Clipping in bright sun scorches the exposed cut surfaces and leaves the piece looking burnt for weeks. Clipping in wet weather spreads blight spores. A dry overcast day is the target.
- Lay a sheet underneath before you start.It makes collecting the clippings trivial, and collecting them matters — box clippings left at the base are a reservoir of blight spores and shelter for pests.
- Work with a guide for formal shapes.A string line for hedging, canes and a template for a ball or a cone. Cut cones and pyramids from the top down and check the outline by standing back frequently. Freehand work drifts, and a topiary piece that has drifted is very hard to correct.
- Keep the base wider than the top.As with any hedge, a slight batter — the sides tapering inwards as they rise — keeps light on the lower growth so the base stays furnished rather than going bare.
- Sweep, collect and bin the clippings.Do not leave them lying and do not compost them if there is any blight in the garden. Bin or burn.
- Disinfect the blades between plants.Box blight moves from plant to plant on tools and on hands. If you have any suspicion of it, disinfect between every plant and clean the tools thoroughly afterwards.
- Feed and mulch in spring.Repeatedly clipped plants are asked to regrow constantly. A slow-release or seaweed feed in spring and a mulch keeps the colour good and the growth dense.
- Reshape a shapeless old plant in mid spring.Box breaks readily from old wood, unlike most conifers. Cut back hard to a smaller version of the shape you want in April or May, feed, mulch and water, and let it refurnish over a season or two. Do one plant or one side at a time in case of a setback.
- Watch for blight and caterpillar all season.Bare brown patches with black streaks on the stems suggest blight; webbing with green and black striped caterpillars inside suggests box tree caterpillar. Both need dealing with promptly and are covered separately.
Tips
- The traditional advice to clip on Derby Day is a useful reminder that the first cut belongs in early June, once the first flush has hardened.
- Single-handed sheep shears give much finer control than two-handed hedging shears on balls, cones and small pieces.
- A box plant clipped every year for decades builds a dense outer shell and a hollow, shaded, twiggy interior. Thinning a few holes into that shell every few years lets light in and keeps it healthy.
- Box is slow. A piece of topiary is years of accumulated work, which is exactly why the hygiene routine is worth the trouble.
Common mistakes
- Clipping in hot sunshine — The cut leaf surfaces scorch and the whole piece browns off for several weeks. A dull day gives a clean green finish.
- Clipping in wet weather when blight is about — Blight spores need moisture to spread and shears carry them from plant to plant. Clip dry, and disinfect.
- Leaving clippings on the ground — They harbour spores and pests at the base of exactly the plant you are trying to protect.
- Clipping into late autumn to tidy up — The soft regrowth is killed by frost and the plant looks brown all winter. Finish by the end of August.
Questions people ask
How often should box be clipped?
Twice a year for a crisp formal finish — early summer and late summer. Once a year in early summer is adequate for a softer look and much less work.
Can I cut old box back hard?
Yes. Box reshoots from old bare wood, so a shapeless plant can be cut back in mid spring to a smaller version of the shape you want and allowed to refurnish. Feed, mulch and water afterwards.
What should I use instead of box shears?
Single-handed shears for detail and small shapes, two-handed shears for hedging, and a powered trimmer only for long runs where the finish matters less.
Is box still worth planting?
In many gardens the combination of blight and box tree caterpillar has made it hard work. There are several good alternatives that clip similarly, which is worth considering before replanting.