Nassella, or needlegrass, is a New World genus of over 100 perennial bunchgrasses found from North America through South America. The Latin word nassa refers to "a basket with a narrow neck". It is usually considered segregate from the genus Stipa and includes many New World species formerly classified in that genus. As of 2011, The Jepson Manual includes Nassella within Stipa. Some species (espeically Nassella neesiana and Nassella tenuissima) are considered invasive pests, as the grass is not properly digested by ruminants.