Ornamental Grasses and How to Prune Them

Image by Margaret Rose Realy, OBL OSB. All rights reserved.

Ornamental grasses are a beautiful garden element; they make a statement in almost any garden with their mass, texture and movement. During the winter season they add interest to a relatively monochromatic landscape.

Ornamental grasses can become unsightly as spring draws near. The smaller-leaved varieties turn into floppy mounds lying on the ground and possibly hiding the flowering bulbs pushing up through the soil. With larger-leaved grasses, the dried leaves begin to break off in the wind and can scatter across the yard. These collapsing mounds can also house mice nests and rabbit forms.

Pruning ornamental grasses is a simple task…though because of the sheer mass of the grass it often looks daunting. Technique is a matter of plant size and personal preference in tools.

The tools you will need also depend on the size of the plant. For smaller jobs I like to use a straight-edge hedge shear with a ratcheting mechanism that increases the power for cutting. I also keep in my pocket hand pruners. When there are a lot of grasses or massive mounds to be pruned, an electric hedge trimmer is easier…just watch out for the electric cord while you work. Some prefer a small chain saw for the tough grasses, like the 12-14 foot Ravennagrass (Saccharum ravennae), and it will be a challenge to cut an inch or two off the ground using this tool. I get a friend competent in handling a chain saw to do the pruning for me.

Binding off a mound of grass is up for debate. Some people use twine, bungee cords, or even good old duct-tape wound around the grass to secure the stack while it is being cut down. This works very well if you are using electric hedge clippers and have a friend to help by holding the stack while you cut. If you do not use the tying method, start on the outer leeward side of tall grasses and cut a section at a time; being downwind allows the cuttings to fall away from where you are working.

Cut as close to the ground as you can. You want to leave only an inch or two of old shoots showing above the soil line. This allows more light to reach the center of the plant where new growth will emerge, increasing the number of new shoots and enhancing plant growth. This severe pruning will also reduce the occurrence of the “donut” effect where the center of the grass mound dies out and new growth only occurs from the outer ring of a living plant. You can maintain healthy clumps for years without division by using this pruning method.

To compost your clippings be sure to chop them up into manageable pieces, otherwise you’ll create a nearly impenetrable snarl. Of course, remove the binding material.

Don’t worry if you are a bit late getting to this task and your ornamental grasses have begun to send up new shoots. More new shoots will continue to rise from the crown and once more give you that bold beautiful look to your landscape.

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