GrassBase - The Online World Grass Flora


W.D. Clayton, M. Vorontsova, K.T. Harman & H. Williamson

© Copyright The Board of Trustees, Royal Botanic Gardens, Kew.

Poa sierrae

HABIT Perennial; caespitose; clumped loosely, or moderately. Rootstock not evident. Cataphylls evident. Rhizomes elongated. Stolons present. Butt sheaths purple. Basal innovations extravaginal. Culms erect; slender; curved; 20–50 cm long. Culm-internodes similar in length; terete (sometimes elliptical); concolorous; ridged; smooth; distally glabrous. Culm-nodes flush with internodes; green; without exudate; glabrous. Lateral branches lacking. Leaves mostly basal; 3–4 per branch. Leaf-sheaths tight; tubular for much of their length; with 0.95 of their length closed; 0.4–3.5 cm long; scaberulous; glabrous on surface. Ligule an eciliate membrane; 3–6 mm long; membranous; translucent; scaberulous on abaxial surface; bilobed, or trilobed; acute, or acuminate. Collar glabrous. Leaf-blades flexuous; tapering towards tip and sheath; involute; 3–15 cm long; 1–3 mm wide; glaucous. Leaf-blade midrib evident. Leaf-blade venation distinct. Leaf-blade surface smooth, or scaberulous; rough adaxially; glabrous. Leaf-blade margins scaberulous. Leaf-blade apex hooded; antrorsely scabrous.

INFLORESCENCE Dioecious (sometimes incomplete). Inflorescence a panicle; comprising 5–8 fertile spikelets.

Panicle open; elliptic; loose; 6–11 cm long; 0.5–3 cm wide; bearing few spikelets. Primary panicle branches 5–8 in number; ascending; 1–3 -nate; indistinct the panicle almost racemose; 0.4–1 cm long; bearing 1 fertile spikelets on each lower branch. Panicle axis differing little from branches; with lower internodes 1.5–3 cm long; scabrous. Panicle branches bearing approximate spikelets; scabrous.

Spikelets ascending; solitary. Fertile spikelets pedicelled. Male spikelets pedicelled; 1 in a cluster. Pedicels 0.5–0.6 length of fertile spikelet.

FERTILE SPIKELETS Spikelets comprising 4–6 fertile florets; with diminished florets at the apex. Spikelets ovate; laterally compressed; (5–)6–7(–8.5) mm long; 3–4 mm wide; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes scaberulous. Floret callus sparsely hairy.

GLUMES Glumes persistent; similar; with lower narrower than upper; shorter than spikelet. Lower glume lanceolate; symmetrical; not clasping; 2.5–3 mm long; 0.75–0.9 length of upper glume; membranous; light green, or mid-green; 1-keeled; 1 -veined. Lower glume primary vein extending to apex; scaberulous. Lower glume surface smooth; glabrous; inner surface glabrous. Lower glume margins flat. Lower glume apex entire; acute. Upper glume ovate; 3–4 mm long; 0.75–1 length of adjacent fertile lemma; membranous; mid-green; 1-keeled; 3 -veined. Upper glume primary vein scaberulous. Upper glume surface smooth; glabrous; inner surface glabrous. Upper glume margins smooth. Upper glume apex entire; acute.

FLORETS Fertile florets appressed to rhachilla; overlapping 0.6–0.8 their length; free at tip; decreasing in size upwards; female. Fertile lemma ovate; symmetrical; laterally compressed; lanceolate in profile; 4–5 mm long; membranous; mid-green; concolorous; keeled; 5 -veined. Lemma midvein simple; pubescent; hairy below. Lemma lateral veins distinct. Lemma surface scaberulous; rough on veins; puberulous to hirsute; hairy at base; hairy on back, or on veins. Lemma apex acute. Palea 4–4.5 mm long; 0.95 length of lemma. Palea keels scabrous. Apical sterile florets resembling fertile though underdeveloped.

FLOWER Lodicules 2; membranous. Anthers 3; 2–2.5 mm long.

FRUIT Caryopsis with adherent pericarp; ovoid; 2 mm long (0.6 mm thick); light brown, or dark brown; striate; acute (subacute). Hilum punctiform.

DISTRIBUTION North America: southwest USA.

NOTES Poeae. Howell 2005.

ADDITIONAL CHARACTERS Conspicuous development of scaly axilliary buds on rhizomes and culm-bases at end of the flowering season; Closed sheaths of upper culm-leaves; Frequent prolongation of ligules of the uppermost leaves into a short scaberulous cylinder.

Please cite this publication as detailed in How to Cite Version: 3rd February 2016.