Plants perennial; cespitose, sometimes rhizomatous. Culms 20-203 cm, solitary or clustered, often rooting at the lower nodes, usually glabrous. Sheaths open, glabrous; auricles absent; ligules scarious; blades flat, margins scabrous, surfaces scabrous or smooth. Inflorescences panicles; branches spreading to ascending; disarticulation below the glumes. Pedicels slightly flared, scabrous to smooth. Spikelets laterally compressed, with 1(2) floret(s); rachillas usually prolonged beyond the florets as a minute stub or bristle, smooth or scabridulous. Glumes from slightly shorter than to slightly longer than the florets, 1-or 3-veined, margins hyaline, keels scabrous, apices acute, sometimes minutely awn-tipped; lower glumes from somewhat shorter than to equaling the upper glumes; florets sessile or stipitate; calluses blunt, glabrous; lemmas 3- or 5-veined, veins often obscure, apices acute, minutely bifid, usually with a short, subterminal awn; paleas 3/4 to nearly as long as the lemmas, 1-veined or with 2 closely spaced veins; anthers 1 or 2. Caryopses often beaked. x = 7. Name of uncertain origin.

Cinna is a genus of four species, all of which generally grow in damp woods, along streams, and in wet meadows. One species, Cinna latifolia, is northern temperate and circumboreal. The other three species are restricted to the Western Hemisphere. Cinna poaeformis (Kunth) Scribn. & Merr. extends from Mexico to Venezuela and Bolivia.

The reduction of Limnodea to synonymy under Cinna by Tucker (1996) introduced a markedly discordant element into the latter genus (Brandenburg and Thieret 2000).

1.   Cinna bolanderi Scribn.
Sierran Woodreed

Culms 85-203 cm; nodes 4-8. Ligules 3.5-7 mm; blades to 40 cm long, 2-19 mm wide. Panicles 7.5-43 cm; branches spreading to ascending. Spikelets (3.6)4-5.5(6.3) mm; rachilla prolongations 0.4-0.9 mm, sometimes absent. Lower glumes (3.3)3.5-5.2(6) mm, 1-veined; upper glumes (3.6)4-5.5(6.3) mm, 1- or 3-veined; stipes essentially absent, florets more or less sessile; lemmas (2.7)3.2-4.6 mm, 5-veined, lateral veins often faint, awns 0.2-1.5 mm or absent; paleas 2-veined, veins very close together; anthers 2, 1.2-2.6 mm, rarely to 0.7 mm. Caryopses 2-2.9 mm. 2n = unknown.

Cinna bolanderi is endemic to meadows and streamsides, at 1900-2400 m, in Sequoia, Kings Canyon, and Yosemite national parks. It flowers from late summer to fall. It used to be included in Cinna latifolia, but it differs from that species in having 2 anthers, longer anthers and spikelets, and sessile florets. The two species do not overlap in distribution.

2.   Cinna arundinacea L.
Stout Woodreed, Cinna Roseau

Culms 28-185 cm, somewhat bulbous at the base; nodes 5-13. Ligules 2-10 mm; blades to 34.5 cm long, 3-19 mm wide. Panicles 6.5-55 cm; branches ascending to spreading. Spikelets (3.5)4-6(7.5) mm; rachilla prolongations 0.1-0.4 mm, sometimes absent. Lower glumes (2.7)3.5-5(6.1) mm, somewhat shorter than the lemmas, 1-veined; upper glumes (3.5)4-6(7.5) mm, equal to or slightly longer than the lemmas, 3-veined, awns 0.2-1.5 mm, or rarely absent; stipes 0.25-0.7 mm; lemmas (2.7)3.5-5(6.4) mm, 3(5)-veined, awns 0.2-1.5 mm or rarely absent; paleas 1-veined; anthers 1, 0.8-1.9 mm. Caryopses 2.1-2.8 mm. 2n = 28.

Cinna arundinacea grows in southeastern Canada and throughout most of the eastern United States, at 0-850 m. It is most common in moist woodlands and swamps, depressions, along streams, and in floodplain and upland woods, and is less frequent in wet meadows, marshes, and disturbed sites. It flowers in late summer to fall. Cinna arundinacea is most easily distinguished from C. latifolia by its 3-veined upper glumes and larger spikelets.

3.   Cinna latifolia (Trevir. ex Göpp.) Griseb.
Drooping Woodreed, Cinna à Larges Feuilles

Culms 20-190 cm; nodes 4-9. Ligules 2-8 mm; blades to 28 cm long, 1-20 mm wide. Panicles 3-46 cm; branches usually spreading, sometimes ascending. Spikelets (2)2.5-4(5.5) mm; rachilla prolongations 0.1-1.3 mm, sometimes absent. Lower glumes (1.8)2.5-4(4.7) mm, 1-veined; upper glumes (1.9)2.5-4(5) mm, 1(3)-veined; stipes 0.1-0.45 mm; lemmas 1.8-3.8 mm, 3(5)-veined, awns 0.1-2.5 mm or absent; paleas 2-veined, with the veins very close together, or 1-veined; anthers 1, 0.4-1 mm. Caryopses 1.8-2.8 mm. 2n = 28.

Cinna latifolia is a circumboreal species, extending from Norway to the Kamchatka peninsula in Russia, and from Alaska to Newfoundland. It grows in moist to wet soil in open coniferous or mixed forests, swamps, thickets, bogs, and streamsides, at 0-2600 m. It flowers in late summer and fall. Cinna latifolia differs from C. arundinacea in its 1 (rarely 3)-veined upper glumes and its smaller spikelets. A collection from the Aleutian Islands had abnormally large (to 5.5 mm) and often 2-flowered spikelets (Brandenburg et al. 1991). Cinna latifolia is a variable species for which varietal names have been proposed; because the variation is continuous, no varieties are recognized in this treatment.