Calamagrostis hillebrandii (Munro ex Hillebr.) Hitchc.

Perennials, Aquatic, leaves emergent, Terrestrial, not aquatic, Rhizomes present, Rhizome elongate, creeping, stems distant, 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 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 2-10 mm wide, Leaf blades mostly flat, Leaf blade margins folded, involute, or conduplicate, Leaf blades mostly glabrous, Leaf blades scabrous, roughened, or wrinkled, L igule 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 branches more than 10 to numerous, Flowers bisexual, Spikelets pedicellate, Spikelets laterally compressed, 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 hairy, Glumes present, empty bracts, Glumes 2 clearly present, Glumes equal or subequal, Glumes equal to or longer than adjacent lemma, Glume equal to or longer than spikelet, Glumes 1 nerved, Glumes 3 nerved, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma similar in texture to glumes, Lemma 5-7 nerved, Le mma glabrous, Lemma apex dentate, 3-5 fid, Lemma distinctly awned, more than 2-3 mm, Lemma with 1 awn, Lemma awn less than 1 cm long, Lemma awn subapical or dorsal, Lemma awns straight or curved to base, Lemma awn once geniculate, bent once, Lemma margins thin, lying flat, 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, Palea about equal to lemma, Palea 2 nerved or 2 keeled, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.

Calamagrostis hillebrandii is a species of grass in the family Poaceae known commonly as Hillebrand's reedgrass. It is endemic to Maui in Hawaii, where there are only two known subpopulations with a total of perhaps 500 individuals. This is a federally listed endangered species of the United States.

Calamagrostis hillebrandii es una especie de hierba de la familia Poaceae. Es nativa de Estados Unidos donde se encuentra en Hawái. Su natural hábitat son los pantanos. Está amenazada por pérdida de hábitat. Los EE.UU. Fish and Wildlife Service ha propuesto recientemente listar esta planta como una especie en peligro de extinción.

Calamagrostis hillebrandii là một loài cỏ thuộc họ Poaceae. Loài này chỉ có ở Hoa Kỳ. Môi trường sống tự nhiên của chúng là đầm lầy. Chúng hiện đang bị đe dọa vì mất môi trường sống.