Densely tufted perennial, with shallow roots and erect stems to 1 m tall. Foliage is tough, unpalatable to livestock, and present nearly year round. Punagrass is often associated with alfalfa fields. The dense clumps can mechanically interfere with mowing. Because it grows faster than alfalfa, infestations are easier to detect 1 to 2 weeks after cutting. Introduced from Argentina. There are other Achnatherum species in South America that closely resemble punagrass and have not been studied in detail. At publication time, the relationships of these species and correct scientific name of California plants are questionable.