When should I cut back herbaceous perennials?
The case for leaving stems standing over winter, the plants that genuinely need cutting in autumn, and how to get both a tidy garden and the wildlife benefit.
- Difficulty
- beginner
- Time
- 1 hr 30 min
- Read
- 3 min
Short answer
Leave most perennials standing until late February. The dead stems shelter overwintering insects, feed birds and protect the crown from frost, and seed heads look far better in winter than bare soil. Cut back in autumn only what is diseased, floppy and slimy, or self-seeding where you do not want it.
The traditional autumn cut-back came from a period when a garden was expected to look bare and swept in winter. The current understanding is that standing stems do real work, and the tidying is better postponed than performed.
What you'll need
- Secateurs or shears
- Gloves
- Rake (optional)
Step by step
- Cut back what is diseased in autumn.Anything with mildew, rust or black spot goes now, and into the bin rather than the compost heap. Leaving diseased material standing carries the problem into next year.
- Cut back what collapses into slime.Hosta, daylily, phlox, oriental poppy and similar soft-leaved perennials turn to a wet mass that rots the crown and shelters slugs. Remove those in autumn.
- Leave anything with structure.Sedum, echinacea, rudbeckia, eryngium, achillea, teasel and ornamental grasses all hold their shape through winter, look good with frost on them and feed birds.
- Leave hollow stems for insects.Many solitary bees and other insects overwinter inside hollow stems. Cutting in autumn removes them; cutting in late February releases them at roughly the right time.
- Leave evergreen and semi-evergreen foliage alone.Hellebores, epimedium, heuchera and bergenia keep working over winter. Hellebore leaves are removed in December or January specifically to show the flowers and reduce leaf spot, which is a different reason.
- Do the main cut in late February.Before new growth is far advanced. Cut close to the ground but above the emerging crown, and take care with plants that shoot early.
- Deal with grasses in early spring.Deciduous grasses such as miscanthus and calamagrostis are cut to the ground in late February or March. Evergreen grasses such as stipa are combed through with gloved hands rather than cut.
- Cut where self-seeding is a nuisance.Alchemilla, verbena bonariensis, aquilegia and fennel will seed everywhere. Cut those before the seed ripens if you do not want a hundred seedlings.
- Compost what you cut.Chopped into shorter lengths it composts far faster. Woody stems benefit from being shredded or bashed first.
- Mulch after cutting back.Late winter is the ideal moment — the bed is clear, the soil is wet and nothing has emerged to be smothered.
Tips
- Leave anything that stands up; cut anything that goes to slime.
- Cutting in late February releases overwintering insects at about the right time.
- Frost on a seed head is one of the few things worth having in a February garden.
Common mistakes
- Cutting everything down in October for tidiness — It removes winter structure, food for birds, shelter for insects, and the frost protection the old growth gives the crown. Very little is gained beyond appearance.
- Leaving mildewed or rusted stems standing — Fungal spores overwinter on the debris and reinfect the new growth in spring. Diseased material is the exception to the leave-it rule.
If it doesn't work
Crowns rotting over winter
Cause: Soft collapsed foliage sitting on the crown — Fix: Cut those species back in autumn and improve drainage around them.
Seedlings everywhere in spring
Cause: Prolific self-seeders left to ripen — Fix: Cut those specific plants before the seed sets next year.
Mildew back every year
Cause: Infected debris left in place — Fix: Remove and bin affected material in autumn, and improve airflow by dividing crowded clumps.
New shoots damaged when cutting back
Cause: Left it too late — Fix: Cut by hand with secateurs around emerging growth rather than shearing the whole clump.
Questions people ask
Is it bad to cut perennials back in autumn?
Not harmful to the plants in most cases, but you lose winter structure, bird food and insect shelter, and some crowns are better protected by their old growth. Late February is a better default.
What should I definitely cut in autumn?
Anything diseased, and anything that collapses into a wet slimy mass — hosta, daylily, phlox, oriental poppy. Also anything self-seeding where you do not want it.
When do I cut ornamental grasses?
Deciduous grasses in late February or March, right down to the ground. Evergreen grasses are never cut hard — comb the dead material out with gloved hands.