Flower:

Branching cluster (panicle) 4 to 10 inches long at the top of the stem, erect to slightly nodding, the main branches erect and hugging the stem, with 2 or more spikelets (flower clusters) per branch. The base of the panicle is often partially hidden in the uppermost sheath. Spikelets are short to long-stalked, single-flowered, 9 to 12 mm (~1/3 to ½ inch) long, narrowly lance-elliptic to spindle-shaped in outline and round in cross-section.

At the base of a spikelet is a pair of bracts (glumes), both similar, thin, hairless, 3 to 5-veined, 9 to 12 mm long, narrowly lance-shaped with a long taper to a slender point at the tip. Florets are surrounded by a pair of bracts (lemma and palea), the lemma thicker than the glumes, 5 to 6 mm long, covered in appressed hairs, narrowly lance-elliptic with a stiff awn ¾ to 1¼+ inches long that is initially straight; the lemma almost completely surrounds the floret, hiding most of the palea. The thickened base of the floret (callus) is covered in appressed hairs.

Leaves and stems:

Leaves are basal and alternate on the lower stem, 1.5 to 3 mm (to 1/8 inch) wide, 4 to 12 inches long, hairless but usually rough-textured, flat or the edges rolled in (involute). Sheaths are hairless except along the edges, with small tufts of long, white hairs at the tip edge where it meets the blade. The ligule (membrane where the leaf joins the sheath) is about 1 mm long, sometimes longer on the upper stem, and rounded or straight across the top edge. Nodes are smooth. Stems are smooth except at the base, erect to ascending or sometimes prostrate from the base and rising at the lower node (geniculate). Plants form loose to tight clumps and may form large tufts.

Fruit:

At maturity, glumes turn pale and translucent and the florets brown, the florets shedding individually leaving the glumes behind on the stalk. The awn twists in response to changes in moisture, coiling and uncoiling as it dries, becoming spirally twisted in part and usually bent twice in the lower half. The panicle branches spread out slightly as the awns twist. Grains (seeds) are golden brown, about 3.5 mm long.

Notes:

Green Needle Grass, formerly Stipa viridula, is the most common species of the genus in North America, found in sandy prairies, railroad rights-of-way, and grasslands of the Great Plains. It reaches the eastern edge of its range in Minnesota and is considered introduced farther east. It is distinguished from other grasses by the appressed panicle branches, single-flowered spikelets, lemmas to 6 mm long covered in appressed hairs with an awn to about 1¼ inch long usually bent twice below the middle, hairless sheath except for a fringe of hairs along the edge plus a few longer hairs at the sheath tip (the collar), membranous ligule about 1 mm long.