Last updated on March 10th, 2022
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Ornamental grasses can be evergreen or deciduous. Knowing how to prune ornamental grasses requires knowing which one of the two you have. Evergreen grasses do not lose their leaves or die back in the winter, and generally just need a quick tidy-up to remove any dead leaves. Deciduous grasses die back to the ground or just turn brown but don’t necessarily die back.
When to Prune Ornamental Grasses
Whether you have evergreen grasses that require some tidying up on occasion or deciduous grasses that need to be cut back annually, you should prune your grasses sometime between early spring in the middle of spring. Pruning is quite easy regardless of what grass you have.
How to Prune Deciduous Grasses
Pruning deciduous grasses that don’t die back
Deciduous grasses are those that turn brown rather than lose any of their leaves so they need to be treated a bit differently when it comes to pruning. Some species, such as the popular Deschampsia ‘Goldtau’ or the Calamagrostis ‘Karl Foerster’ need to be pruned all the way to ground level at the beginning of spring so that new growth has an opportunity to spring forth, no pun intended.
Other deciduous grasses that produce their new growth later in the spring can be pruned as late as April. You can also prune late for those that have structural stems remaining over winter, in which case you remove the structural stems so that the newer, greener shoots are able to develop.
There are some varieties of deciduous grasses that share traits with evergreen grasses because they build up a lot of dead material. If you have one of these in your garden you can simply comb out the loose foliage and cut back any of the dead material in the spring.
How to prune back deciduous grasses
When your deciduous grasses are ready for pruning, cut back any of the spent stems, taking care that you don’t damage any of the new, greener growth that could be making its way through the crown. If there are stems and debris near the middle of the clump you can pull those out by hand, again being careful not to damage new shoots.
As you continue this process it’ll be easier for you to see what you’re doing with the damaged, spent stocks and flowers removed. This will make it less likely that you will damage the younger shoots. Remove any dead leaves or debris from around the crown and remove any nearby leaves. When you are done you can add some mulch to the crown as well as a general fertiliser such as growmore to help it replenish itself.
How to Prune Evergreen Grasses
If you have smaller evergreen grasses you can trim them back come spring. For this, you want to remove any tips that are brown and cut back any dead leaves that you might find along the base. Evergreens don’t need hard pruning like other plants, but rather do well with simple trimming and tidying up here and there. Some of the different sedges should not be cut back completely but instead have the spent flower stalks removed, similarly to deadheading. Any leaves that are scorched or diseased should be removed as well.
With evergreen grasses, there are specific varieties that benefit from a hard annual pruning, one being the pampas grass. This grass should be cut back as much as you can without damaging any new growth, although when you do so you need to wear pants, long sleeves, thick gloves and eye protection because the blades on each leaf have very sharp edges.
If you have an evergreen that has outgrown the space it was planted you can divide it the same as you would divide any other perennial, then remove any debris and then replant your divisions.