Ornamental Grasses

#TeachingTuesday: Ornamental Grasses

Ornamental grasses are a very large and diverse group of plants. A few examples are maiden grass (Miscanthus spp.), fountaingrass (Pennisetum spp.), switchgrass or panicgrass (Panicum spp.), muhly grass (Muhlenbergia spp.), and Mexican feather grass (Nasella tenuissima). Ornamental grasses provide a wide range of sizes, shapes, colors, and textures to add to the landscape, and they look great almost all year, with just a brief rest period in the late winter after they are cut back. One of the most elements that grasses can add to a design is movement—when the wind blows through them, it creates an image almost like flowing water. In the fall when they go dormant, they turn a light tan or golden color, but typically maintain a nice shape unless they get beaten down by excessive rain or snow.

Almost all ornamental grasses prefer full sun and well-drained soil. They will not tolerate wet soils, and if they receive too much shade, they will flop over and eventually die. However, in the right location grasses are unbeatable performers, with few pest and disease problems. They do not typically need fertilizer, and in fact, too much fertilizer will cause them to flop over like shade.

Left: Mexican feather grass in foreground, Russian sage in background. Right: Close-up of feather reed grass.

Maintenance Tips

Make sure to keep ornamental grasses watered adequately through the first year after planting, even in the winter. One they are established, they are very low maintenance. Most grasses should be cut back once a year in the late winter, just before they start growing again (typically January-February in NC). Check the crown for signs of new growth, and then cut back the old foliage to anywhere from 3-18” above the ground, depending on the size of the plant. Some grasses have very sharp leaf blades, so make sure to wear long sleeves and gloves for this process.

Some Similar Plants

Carex, or sedge, is a grass-like plant that may be easily confused as an ornamental grass. Because they are much slower growing, they should not be cut back in the winter unless the leaves have severe cold damage (browning). How can you tell a sedge and a grass apart? Cut and look at the base of a stalk. If it’s triangular, it’s a Carex, if it’s hollow, it’s a grass. If it’s solid and round, it’s most likely a member of a third group called rushes. Rushes are less common, but do grow in NC.

Lirope (also known as monkey grass) and mondo grass (Ophiopogon spp.) are also grass-like, but are not related to grasses, sedges, or rushes. They are actually both in the asparagus family! Liriope grows quickly, and can be cut back in the late winter, but mondo grass is much more slow-growing and should not be cut unless there are a lot of dead leaves. Please see our earlier post about the differences between liriope and mondo grass here.