Old growth provides winter structure and homes for predators
When I was younger, one of the hard and fast rules was cut back herbaceous perennials in autumn, leaving a very bleak soilscape until the new growth in spring.
However, things have become a little more enlightened, as we think more about the wider ecology of our gardens and less about how tidy we are.
If you are a fanatic about order and can’t stand to see dead stems in your borders, bear this in mind – you are removing vital homes, habitats and food for wildlife, especially helpful predators that will eat pests next summer.
There’s also the lack of winter interest, height and structure – imagine missing frosted stems in the early morning before you go out to work?
If you’re actively looking for winter interest, try the dried flowerheads of teasels, cardoons (Cynara), globe artichokes, Sedum spectabile, Eryngium (sea holly), Phormium (New Zealand flax) and the foliage and flowers of ornamental grasses.
Some of the few plants old-school gardeners did leave over winter were borderline hardy perennials such as penstemons, Knifophia (red hot pokers – it’s slightly different, with evergreen foliage tied in a topknot to cover the crown) and ornamental sedges, so the old stems protected the crown from frost.
Evergreen perennials such as Kniphofia and ornamental sedges are not cut back but are tidied during spring and summer by removing dead foliage.
Cutting back herbaceous perennials in spring
- From March onwards, more care is needed, as new growth will probably have started.
- Using a knife, shears or secateurs cut stems close to the crown, avoiding the new shoots.
- Tidy up the base of the plant, mulch and feed with a general fertiliser, such as Growmore.
Cutting back early-flowering perennials
Perennials and rock plants, such as geraniums (cranesbills), delphiniums and Aubretia are cut to near ground level after flowering to encourage new foliage and another flush of flowering.