Stipa richardsonii Link

Perennials, Terrestrial, not aquatic, Stems nodes swollen or brittle, Stems erect or ascending, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly basal, below middle of stem, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades very narrow or filiform, less than 2 mm wide, Leaf blades 2-10 mm wide, Leaf blade margins folded, involute, or conduplicate, Leaf blades mostly glabrous, Leaf blades scabrous, roughened, or wrinkled, Ligule present, Ligule an unfringed eciliate membrane, Inflorescence terminal, Inflorescence an open panicle, openly paniculate, branches spreading, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence lax, widely spreading, branches drooping, pendulous, Flowers bisexual, Spikelets pedicellate, Spikelets dorsally compressed or terete, Spikelet less than 3 mm wide, Spikelets with 1 fertile floret, Spikelets solitary at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating above the glumes, glumes persistent, Spikelets disarticulating beneath or between the florets, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 2 clearly present, Glumes equal or subequal, Glumes equal to or longer than adjacent lemma, Glumes 3 nerved, Glumes 4-7 nerved, Lemma coriaceous, firmer or thicker in texture than the glumes, Lemma 5-7 nerved, Lemma body or surface hairy, Lemma apex acute or acuminate, Lemma distinctly awned, more than 2-3 mm, Lemma with 1 awn, Lemma awn 1-2 cm long, Lemma awn 2-4 cm long or longer, Lemma awned from tip, Lemma awn twisted, spirally coiled at base, like a corkscrew, Lemma awn twice geniculate, bent twice, Lemma margins inrolled, tightly covering palea and caryopsis, Lemma straight, Callus or base of lemma evidently hairy, Callus hairs shorter than lemma, Palea present, well developed, Palea membranous, hyaline, Palea shorter than lemma, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.

Achnatherum richardsonii is a species of grass known by the common names Richardson's needlegrass, spreading needlegrass, and Canada mountain-ricegrass. It is native to northwestern North America, where it is distributed from Alaska and Yukon through the western Canadian provinces south to Colorado.

This is a tufted perennial bunchgrass growing up to a meter tall. The inflorescence is open with spreading branches. The spikelet has a twisted awn up to 2.5 centimeters in length.

This grass grows in several habitat types, including grasslands, meadows, and pine forests. It can be found on moraines, plains, and mountain slopes. It is a dominant or codominant grass species in some areas, such as the western Canadian grasslands and the climax plant communities of Glacier National Park. Plants associated with it include Canada bluegrass (Poa compressa), prairie Junegrass (Koeleria cristata), rough fescue (Festuca altaica), Idaho fescue (F. idahoensis), bearded wheatgrass (Elymus caninus), western needlegrass (Achnatherum occidentalis), timber danthonia (Danthonia intermedia), tufted hairgrass (Deschampsia cespitosa), sedges (Carex spp.), shrubby cinquefoil (Potentilla fruticosa), bearberry (Arctostaphylos uva-ursi), timothy (Phleum pratense), common yarrow (Achillea millefolium), prairiesmoke avens (Geum triflorum), northern bedstraw (Galium boreale), Hood's phlox (Phlox hoodii), and bluebell (Campanula rotundifolia).

This grass is a common food source for livestock and wildlife such as elk and bighorn sheep on the Great Plains. It is preferable when young because as it matures, the fruits become hard and sharp.

Stipa richardsonii là một loài thực vật có hoa trong họ Hòa thảo. Loài này được Link miêu tả khoa học đầu tiên năm 1833.