Nassella tenuissima aka Mexican Feather Grass

Nassella tenuissima is a perennial grass in the Poaceae family. Gardeners know it as Mexican feather grass or Texas needle grass. Its former name is Stipa tenuissima. It comes from New Mexico, Texas, Mexico, and Argentina. Plants stay evergreen in their native desert regions. In colder gardens, growers may use them as annuals. The RHS describes its foliage as deciduous in Britain.

This grass forms a dense tuft with upright, arching growth. Garden plants stand about 1–2 feet (0.3–0.6 metres) tall. The RHS gives an upper height of 3.3 feet (1 metre). Clumps spread about 1–2 feet (0.3–0.6 metres) wide. The thin green leaves curl inward along their edges. They move in light wind and turn tan in winter. Their smooth blades have no hairs and exceed six inches long. Upright green stems also turn tan as they age.

Small flowers grow in loose, feathery panicles above the leaves. Chicago records flowering in May and June. Other sources describe a summer display that lasts into fall. The heads change from green to silver, yellow, or pale brown. Each flower measures less than an inch across. The fruit is a dry grain called a caryopsis. Seed heads carry thin brown bristles and produce thousands of seeds. Tan seed heads remain visible in fall.

Grow this grass in full sun and soil that drains well. It also accepts some shade, according to NC State. It grows in sand, loam, clay, and shallow rocky ground. The RHS lists acid, neutral, and alkaline soils as suitable. It tolerates drought, though heat and drought may trigger dormancy. Hot, humid conditions in the southeastern United States suit it poorly. Sources give USDA zones 7–9 or 7–10. The RHS rates it H4 for Britain. Cut dead leaves back in early spring rather than late fall. Grow new plants from spring-sown seed or divide clumps in spring.

Its fine leaves add contrast to borders and rock gardens. Sources also list containers, mass planting, and erosion control as uses. Deer tend to leave it alone. Aphids and leaf spot can occur despite its low disease burden. Wet ground can cause root or crown rot. Heavy self-seeding lets it escape gardens. Sources report invasive growth in Australia and California. Check local rules before planting it. The supplied evidence does not establish edible uses or toxicity.