Nassella tenuissima is a graceful, delicate and very fine textured ornamental grass. It grows in a dense fountain like clump with slender, wiry culms 0.3-0.6m tall. The leaves are 15.2-35.6cm long, 0.5mm wide, rolled inward very tightly so that they appear as thin wiry filaments (Christman, 2004). It blooms in late spring with a greenish flower cluster that persists well into fall as it ripens to golden brown (Christman, 2004). Flowers grow in unequal size; a single bisexual floret, which is longer than the floret; flower head, is often only partly exerted and spread from the end (DPI, 2004). Silvery inflorescence between summer to fall and becomes light straw coloured in fall (Evans, 2000). The main body of the seed is 2 to 3mm long DPI (2004). Young seedheads held among the leaves; mature seedhead to 25cm long; glumes to 1cm long; callus bearded (AWC, 2004).

Australian Quarantine in 1998 permitted the legal import of Nassella tenuissima despite all Nassella species are prohibited, because of a slip related to the species synonym. The importer used its old taxonomic name, Stipa tenuissima, in the import proposal, which was permitted.

In La Pampa, Argentina, Nassella tenuissima vegetates in autumn, flowers in November and sets seed in December-January (Freda Anderson., pers.comm., 2005).

In Argentina Nassella tenuissima is being used as an ornamental and in some provinces like Tucumán it is used as thatch (F. Anderson, pers. obs.).
Species of a low nutritional value, with a high fibre content which animals do not consume; its abundance indicates degradation of the pasture (de Agrasar et al 2005).

Nassella tenuissima grows on well drained soil and is very drought tolerant (Christman, 2004).

Nassella tenuissima produces thousands of seeds, which are dispersed by wind, water or contaminated soil. Usually propagated from seed and often self sows (Evans, 2000; Christman, 2004).

Used as an ornamental and sold in nurseries (AWC, 2004).

The plant was introduced into Australia and marketed in nurseries under the names “elegant spear grass”, “pony tail” and ”angel's hair”. Education about its negative impacts and the destruction of existent plant specimens in gardens and nurseries could prevent this weed from becoming introduced into new countries or regions in the future.