How and When to Cut Back Ornamental Grasses
The garden plants known collectively as ornamental grasses include dozens of species that are valuable in the garden as landscape plants. Most are perennial plants with grasslike appearance and growth habits, grown for the appeal of their foliage rather than their blossoms. While some are true grasses (Poaceae family), there are also sedges, rushes, and other plants that are commonly included in this category.
These plants add unique texture, form, motion, and even sound to the garden as they rustle in the breeze. And because many ornamental grasses are native species, they're favored among gardeners who are interested in natural and water-efficient landscaping. But once the foliage turns brown, the foliage will need to be removed. Removing dead ornamental grass can be a messy job, but there are some best practices to make the work easier and tidier.
When to Cut Back Ornamental Grasses
When to cut back your ornamental grass is governed by the type of grass and your personal preference. You can do the job in the fall after the foliage dies, or leave it in place through the winter and cut it back in the spring.
Some ornamental grasses will remain attractive through the better part of the winter. And at a time when the rest of the landscape is rather dreary, long grasses swaying in the breeze can add some visual interest. Plus, their seed heads can provide food for wildlife.
If you live in a region where wildfires are endemic, use ornamental grasses with caution. Rather than allowing the dead grasses to remain for their ornamental appeal, it's best to remove the foliage promptly at the end of the growing season. Few plants burn more fiercely than a large clump of dried grasses. When planting ornamental grasses, keep them well away from your home and other structures. In some regions, authorities now caution against planting ornamental grasses at all—as well as any other plants likely to burn easily.
Before Getting Started
Ornamental grasses are grouped into three categories: warm season, cool season, and evergreen. Some evergreen "grasses," including seges and carex, aren't really in the grass family, and these don't need pruning (though they can be divided if they get unruly). But how do you know which type of ornamental grass you have, and when to prune it?
Cool season grasses grow primarily in spring before the temperatures exceed 75 degrees Fahrenheit, and in fall when temperatures cool. These grasses keep their color throughout the heat of summer without much growth. Cool season grasses should be cut back in very early spring. As soon as the snow clears, cut the grass back by two-thirds, leaving one-third in place. Pruning too drastically can harm the plant. Some examples of cool season grasses include fescues, blue oat grass (Helictotrichon), tufted air grass (Deschampsia), and autumn moor grass (Sesleria).
Learn How to Cut Back Ornamental Grasses in Spring and Fall
Warm-season grasses begin growing in mid to late spring, or even early summer. They thrive when the temperatures rise, with major growth and flowering occurring during summer's heat. Warm-season grasses turn brown in winter. If you prefer a tidy garden, or if your ornamental grass is a variety that doesn't look great dormant, cut back these grasses in fall. However, many grasses add terrific winter interest in the landscape, adding movement and texture when much of the garden is asleep. If you want to keep some interest in your garden throughout the winter, cut back these grasses in mid to late spring.
When you prune these warm-season grasses, cut them severely, right down to the ground. Some common warm-season grasses include northern sea oats (Chasmanthium), Japanese silver grass (Miscanthus sp.), hardy pampas grass (Erianthus), perennial fountain grass (Pennisetum), switchgrass (Panicum), and prairie cordgrass (Spartina).
What You'll Need
Equipment / Tools
- Pruning shears or a power hedge trimmer
- Lawn rake
- Biodegradable tape or bungee cords
Tie Grass Into Bundles
The fuller the ornamental grass is, the messier it can be when cutting it down. To lessen the mess, start by bundling the stalks. Wear gloves—some grass blades can be quite sharp. Any wide tape will do, as long as it's sticky enough to adhere to the grass. Biodegradable paper tape is recommended for an eco-friendly approach. As an alternative, many gardeners like to use reusable bungee cords stretched tightly around the grass.
Depending on the height of the ornamental grass, you might need to wrap each bundle of grass in two or three spots along the length of the stems. And especially wide plants might need to have their stalks divided into two or more sections before bundling.
Cut the Grass
Now that the ornamental grass is neatly bundled, use pruning shears to cut the grass, either by two-thirds for cool-season grass or to ground level for warm-season grass. With the tape or bungee cords holding the grass blades in place, lean the bundle away from its base as you cut.
If your ornamental grass is thick, a power hedge trimmer might be helpful to do the job. Either way, aim to keep the bundle intact as you cut.
Finish the Job
Cutting each grass bundle is the bulk of the job. But there will undoubtedly be a few renegade blades outside of the bundle to clean up with pruning shears. Finish by raking the garden area to catch any loose blades of grass.
Grass that has been bundled with biodegradable tape or string can be easily tossed whole into a compost heap or municipal lawn waste site. If you have used vinyl tape, make sure to remove the tape as you dispose of the grass bundles.
Should ornamental grasses be cut back for winter?
If you have an ornamental grass species that remains attractive through the winter, it’s often best to leave it in place. However, if the foliage of your species depreciates at the end of the season, you can go ahead and cut it back in the fall.
What happens if you don't cut back ornamental grasses?
If you don’t cut back your ornamental grasses, they not only might look untidy with depreciated foliage, but they also might spread their seeds in unwanted areas. Plus, fresh foliage in the spring might have a difficult time growing through the depreciated foliage.
How far back do you cut ornamental grasses?
How far you cut back your ornamental grasses depends on the species. Cool-season grasses can be cut back by around two-thirds of their length while warm-season grasses can be cut to nearly ground level.
Maintenance of Ornamental Grasses. University of Illinois Extension