How to cut back
Deciduous grasses, which turn a golden, straw brown rather than necessarily lose their leaves, need different treatment from those with are evergreen.
Deciduous grasses
- Some deciduous species, for example Calamagrostis × acutiflora 'Karl Foerster' and Deschampsia cespitosa 'Goldtau' should be trimmed to ground level before growth starts in early spring. Other deciduous grasses, such as Pennisetum orientale, do not produce new growth until later in the season. The culms (old stems) will protect the crown, so delay clipping these types until late April
- Pruning late (mid-March to April) is also appropriate for Miscanthus, which has structural stems that persist over the winter. These should be pruned away individually with secateurs to ensure the new, green shoots are not cut off in the process
- Stipa tenuissima is classed as deciduous but in some gardens performs more as an evergreen. If the build up of dead material is low, treat as for evergreens by simply combing out the loose foliage. Alternatively, and for plants with a lot of dead, cut back fully in spring
Evergreen grasses
- Small evergreen grasses, such as Festuca glauca, can be trimmed in spring. Remove any brown tips and cut back the dead leaves that usually collect around the base
- Larger evergreen species such as Cortaderia selloana (pampas grass) benefit from hard annual pruning in early spring, cutting back as far as possible without damaging new growth. Wear goggles and thick gloves as leaf blades have sharp edges, and cut tough stems with loppers. Burning pampas grass is no longer common practice as the crown can be damaged. Removing a large unwanted pampas is no easy matter and may require machinery such as a mini-digger if digging around with a spade or mattock fails to lift it
- Evergreens such as sedges (Carex and Luzula) are not cut back completely like deciduous grasses. Spent flowering stalks can be cut off, and any unsightly scorched or diseased leaves can be removed individually
- Once the clump outgrows its space, you can divide it as you would any other perennial. Debris can be removed, the area tidied, and mulched with organic matter and fertiliser spread as for deciduous grasses