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.
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.
After cutting back, mulch and fertilise to promote growth and flowering.