Pruning Yarrow
When and how — Achillea millefolium
Prune your yarrow in March and November — the optimal month is usually November.
The next pruning window is November.
When to prune?
The perennial yarrow is pruned in March and November.
With perennials, pruning is really seasonal management.
You don't prune perennials the way you prune shrubs. The work happens at three moments: (1) deadheading spent flower stems during the season to encourage repeat bloom, (2) optionally cutting back to about 10–15 cm above ground in late autumn, and (3) clearing all the old foliage in March before the new shoots emerge. Many gardeners now deliberately leave the old growth standing through winter — it protects the crown and shelters overwintering insects. Which approach to choose depends on taste and species: evergreen perennials (hellebore, bergenia) look better left alone, while wet-rotting species (hosta) need to come down after the first frost.
How to prune yarrow
Yarrow doesn't require heavy pruning, but a couple of well-timed cuts will keep plants tidy, encourage repeat flowering, and prevent excessive self-seeding. The main pruning window is March and November, though deadheading through the flowering season is equally important. In March, cut back any old stems you left standing over winter. Trim the whole plant down to just above the basal foliage—usually about 5–10 cm from the ground. This removes tatty growth and makes way for fresh shoots. Use clean secateurs or garden shears; yarrow stems are tough when dry, so sharp tools make the job easier. If you didn't cut back in autumn, March is your chance to tidy up before new growth begins in earnest. During the flowering period from June to August, deadhead spent flowerheads regularly. Snip them off just above a set of leaves or side shoots. This not only keeps the plant looking smart but often triggers a second, lighter flush of blooms later in summer. If you want yarrow to self-seed in informal areas, leave a few flowerheads to set seed in late summer, but be aware it can spread enthusiastically. In November, once flowering has completely finished and foliage begins to die back, cut the plant down to ground level again. Some gardeners prefer to leave the seedheads standing for winter interest and wildlife, then tidy up in early spring instead—both approaches work well. Yarrow is forgiving and bounces back reliably whichever schedule you choose.
Common mistakes
✗ Cutting back too early in spring
Late frost can still strike and the old foliage protects the crown. Wait until the first new shoots are visible (usually mid-March) — then you know the season has actually started.
✗ Skipping deadheading
Hardy geranium, salvia, lupin and delphinium will give a second flush if you cut spent stems back to just above a pair of healthy leaves as soon as the first flowers fade.
✗ Cutting ornamental grasses down in autumn
The dry stems are the whole point of winter interest, AND they protect the crown from frost and waterlogging. Cut down to a fist's height only in late February.
Hold off on pruning
Better to wait than prune at the wrong moment. The next optimal window is November. Until then: leave the plant alone — only remove dead or diseased wood (which you can do year-round).
