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Info
Subfamily: Pooideae
Genus etymology: Calamagrostis = "reed grass" [Greek] refering to the habit of many members
Species etymology: expansa = "expanded" [Latin] refering a panicle which is an open inflorescence. Clifford & Bostock 2007 state that this is an orthographic error of "inexpansa" meaning "unexpanded" [Latin]. Hillebrand gives no comments about the name
Photosynthetic type: C3 (cool season)
Nativity: endemic
Legal status: Hawaii DLNR - Endangered
Map
Inflorescence
image credit: Ken Wood
image credit: Ken WoodPlant
image credit: Ken Wood
image credit: Ken WoodDescription
Robust perennials, short-rhizomatous; culms erect or sometimes decumbent, 5-20 dm tall, 4-8 mm in diameter. Sheaths overlapping rather closely along the middle of the culm, minutely retrorse-scaberulous, margins membranous, throat sparsely pubescent; ligule membranous to chartaceous, 3.5-4 mm long, puberulent, apex triangular to rounded, erose; blades flat to involute, firm, 15-20 cm long, 1-3 cm wide, the uppermost reduced, upper surface scabrous and plicate, lower surface glabrous, apex indurate, hard-pointed. Inflorescences paniculate, oblong, contracted, 15-30 cm long, densely scabrous, the branches ascending, loosely appressed to axis, devoid of spikelets on lower 1/2 of branch, rachilla 1.5-2 mm long, obscured by long whitish yellow silky hairs up to 1 cm long; glumes equal, pale, persistent, longer than floret, spreading, slightly recurved, ca. 7 mm long, scabrous on keel and otherwise scaberulous, apex acuminate, first glume 1-nerved, second glume 3-nerved, nerves green; lemma thin, chartaceous to membranous, 4-4.5 mm long, 5-nerved, nerves green, scabrous, callus thickened, hardened, densely silky pubescent, the hairs 4-5 mm long, encircling floret, apex 4-toothed, the teeth slender, midnerve produced into an awn 7-10 mm long; palea 2.5-3 mm long, 2-nerved, scabrous, acuminate. Caryopsis pale brown, ovoid, 2-2.5 mm long, slightly grooved ventrally, apex apiculate.
(Description source: O’Connor, P.J. 1990. Poaceae, pp. 1481–1604. In: Wagner W.L., Herbst D.R. & Sohmer S.H. (eds.)., Manual of the flowering plant of Hawaiʻi. Vol. 2. University of Hawaii Press & Bishop Museum Press, Honolulu )