Join the RHS today and support our charity
Free personalised gardening advice
RHS members get reduced ticket prices
RHS members get free access to RHS Gardens
Reduced prices on RHS Garden courses and workshops
020 3176 5800
Mon – Fri | 9am – 5pm
Help us achieve our goals
Make a donation
I have forgotten my password
Keep me signed in
Register for free to receive our newsletters, add comments to blogs/articles and to save content.
See what events are on near you and browse your bookmarked pages.
Inspiring days out and so much more
Perennials are not demanding plants, but trimming them after flowering finishes in autumn helps improve their appearance and flowering. However, you can leave some stems over winter to provide homes and food for wildlife, and then trim back in spring.
All herbaceous perennials and ornamental grasses that die back to soil level.
Cutting back herbaceous perennials during autumn restores order and tidiness to the garden. However, this removes potential winter interest, in the form of height and structure, plus food and habitat sources for wildlife so many gardeners delay the cut back until spring.
Selective cutting back in autumn can retain the dried, bleached flowerheads of plants, while removing material showing signs of decay or fungal growth. Examples include: such as Sedum spectabile (ice plant), Eryngium (sea holly), Phormium (New Zealand flax) and the foliage and flowers of ornamental grasses.
More tender plants with woody stems, such as penstemons, are left so that the old stems protect the crown from frost. Leave pruning of these and other borderline-hardy perennials until the risk of frost has passed – usually April or May.
Evergreen perennials such as certain Kniphofia and ornamental sedges are not cut back, but are tidied during spring and summer by removing dead foliage.
After cutting back, mulch and fertilise to promote growth and flowering.
Although the general principles are the same, there are a few differences depending on what season the work is carried out. This is explained below.
Many gardeners choose to leave dead herbaceous plants and grasses over winter to provide structure to the garden, as well as food and shelter for wildlife. However, more care is needed when cutting back in spring to avoid damaging new shoot growth. Most gardeners start cutting back from March onwards:
Early-flowering perennials such as geraniums and delphiniums are cut to near ground level after flowering to encourage fresh foliage and late summer flowering. These are then cut back again in autumn or spring.
Sometimes gardeners are caught out by earlier-than-expected growth of perennials in spring. In these cases, rather than cutting out new growth, merely tidy up the plants by pulling out dead stems.
In very wet winters, the soil can be too wet to access plants without compacting soggy soil. Rather than damaging the soil, it is best to wait until it is drier in spring; and then tidy up the plants by pulling out dead stems. Where soils are prone to waterlogging and damage, carry out cutting back in autumn.
AgapanthusBorders: revitalising an over-mature bedDeadheading plantsOrnamental grasses PerennialsPerennials: dividingPerennials: plantingPerennials: stakingPenstemonsVideo: cutting back perennials
the RHS today and get 12 months for the price of 9
RHS members can get exclusive individual advice from the RHS Gardening Advice team.
Register for the site or sign in to share your experiences on this topic and seek advice from our community of gardeners.
anonymous on 12/09/2014
is it best to deadhead agapanthus after flowering?
This comment has been reported and is currently under moderation.
We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.
Join the RHS today and get 12 months for the price of 9