It sounds too good to be true: an ornamental grass that loves heat and looks beautiful all year gently swaying in the wind. But threadgrass (Nasella tennuissima) fits the bill — and is waterwise. This pretty low-water plant also is called silky thread grass or Mexican feather grass.
Texture and movement can add to a garden’s design nearly as much as shape and color. Threadgrass has a delicate, windswept form that serves as an attractive backdrop to low-growing flowering plants like sedums or verbena. In summer, the grass is a nice green with feathery ends. In winter, the airy flower heads take on a golden, wheat-like appearance. Threadgrass is deer resistant, has no known diseases or pests, and is a native plant that grows in zones 5 through 10.
Plant threadgrass in spring, summer or fall. Because it likes heat, you might be able to fill in a summer bare spot with threadgrass after weather is too hot for most garden plants. If you want a swaying meadow effect, you’ll need to plant a few, and then wait for them to reseed. If you want immediate effect, plant several. Just keep in mind the plant grows to about 12 inches wide.
Your threadgrass plants should reach about 18 to 24 inches high when fully grown, sometimes higher when blooming. Plant it in full sun and in most any kind of soil. When you first plant or transplant your threadgrass, give it a little extra water, especially in high heat.
Caring for Threadgrass
Once threadgrass is established, it should need nothing but rain water to grow and set seed. The plant is a short-lived perennial and should come back several years in a row, assuming typical low temperatures for the lower zones. It also reseeds (see below), creating new plants nearby. You can leave these to eventually replace the established ones, or dig them up and transplant them to another spot in your garden. They are easy to recognize.
Each spring, as you begin pruning other plants in your garden, gently comb the grass blades with a fine rake and trim them for shape.
Caution for Some Gardeners
The fact that threadgrass replaces itself by sprouting tiny plants from seed is a bonus to me. We get just enough seedlings to move around our garden, without them being a problem. But in some areas, threadgrass can be invasive, reseeding in places where it interferes with other plants. In fact, the plant is prohibited in California because it is so invasive there and can crowd out grasses native to coastal areas. It also can crowd out pasture grasses. We have had no problems with that, however, and have only seen the plants pop up near mature ones.
Not sure yet? Check out the short video of the grass moving in the winter breeze I posted on Southwest Gardening Blog’s Instagram page.
Enjoy growing threadgrass and other ornamental grasses in your low-water garden!