Ornamental grasses: cutting back
Ornamental grasses fall into two main groups, evergreen and deciduous. Deciduous grasses need cutting back annually, so they look their best. Evergreens usually just require a quick tidy-up.
- Deciduous grasses – cut them back to the base
- Evergreen grasses – usually only need the dead material removing and don’t always respond well to hard pruning
When to cut back
Early to mid-spring, depending on the species. Ornamental grasses provide attractive structure over winter, so wait until spring to cut back deciduous types, but aim to get it done before new shoots start to emerge.
Most deciduous grasses start to sprout in early spring, but a few (such as Pennisetum orientale) are slower to get started. With these, the old stems will protect the crown from cold weather, so delay clipping until late April. Late pruning (mid-March to April) is also appropriate for Miscanthus.
How to cut back
Deciduous grasses, which turn a golden or straw-brown rather than necessarily losing their leaves, need different treatment to evergreen grasses.
How to cut back deciduous grasses
The aim is to remove all the old stems and foliage completely, to let the new stems emerge and form a fresh display, unhindered by old growth
Work your way through the clump, cutting the old stems as low down as possible, using sharp secateurs. Also pull out any loose stems and other accumulated debris
Try to avoid damaging any new growth that may already be starting to emerge
Stipa tenuissima is classed as a deciduous grass, but in warmer regions it often performs more like an evergreen. If there’s little build-up of dead material, then treat it as an evergreen and simply comb out the loose foliage. But if there is a lot of dead material, cut it back fully in spring
How to tidy up evergreen grasses
- With most small to medium-sized evergreen grasses and sedges (such as Carex and Luzula), simply pull out all the dead leaves, old flower stems and accumulated debris by hand. Comb them out with your fingers and/or use a rake. Any dead leaves or stems that are still firmly attached may need to be cut off individually, but don’t remove the living, green foliage
With Festuca glauca and similar dense clumps, make sure you remove all the dead leaves that usually collect around the base, along with any brown leaf tips, to keep them looking their best
Larger evergreen species (such as pampas grass, Cortaderia selloana) benefit from hard pruning annually in early spring. Cut them back as far as possible without damaging the new growth. Wear eye protection and thick gloves as the leaf blades have sharp edges. Cut tough stems with loppers. Burning pampas grass is not advisable, as the crown can be damaged
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