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 stebbinsii

HABIT Perennial; caespitose. Basal innovations extravaginal. Culms erect; slender; straight; (6–)10–30(–40) cm long. Lateral branches lacking. Leaves mostly basal. Leaf-sheaths open for most of their length; with 0.2–0.4 of their length closed. Ligule an eciliate membrane; (2.5–)3–6 mm long; hyaline, or membranous; translucent; glabrous on abaxial surface; lacerate; obtuse, or acute, or acuminate. Collar glabrous. Leaf-blades conduplicate, or involute; (5–)6–15 cm long. Leaf-blade venation distinct; comprising 7–9 vascular bundles. Leaf-blade surface smooth, or scaberulous, or scabrous; rough adaxially; glabrous, or puberulous.

INFLORESCENCE Inflorescence a panicle. Peduncle 3–20(–29) cm long.

Panicle open, or contracted; lanceolate to ovate; loose; straight; (2.4–)3–6.5(–7.2) cm long; bearing few spikelets. Panicle branches terete, or angular; scaberulous; rough throughout.

Spikelets ascending; solitary. Fertile spikelets pedicelled. Pedicels 2–5 mm long.

FERTILE SPIKELETS Spikelets comprising 2–4 fertile florets; with diminished florets at the apex. Spikelets oblong; laterally compressed; 5.3 mm long; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes 1 mm long; smooth, or scaberulous. Floret callus glabrous.

GLUMES Glumes persistent; similar; shorter than spikelet; thinner than fertile lemma, or similar to fertile lemma in texture; shiny. Lower glume lanceolate; 2.5–4 mm long; 0.85–0.95 length of upper glume; membranous; 1-keeled; 3 -veined. Lower glume primary vein scabrous. Lower glume apex acute. Upper glume elliptic; 2.7–4.7 mm long; 0.72–0.9 length of adjacent fertile lemma; membranous; 1-keeled; 3 -veined. Upper glume primary vein scabrous. Upper glume surface scabrous; rough on veins. Upper glume apex acute.

FLORETS Fertile florets bisexual (sometimes female). Fertile lemma ovate; dorsally convex along back; ovate in profile; 3.7–4.4–5(–5.5) mm long; membranous; keeled; 5 -veined. Lemma midvein without distinctive roughness, or scaberulous; eciliate, or ciliolate. Lemma lateral veins evenly spaced. Lemma surface smooth to scaberulous; glabrous. Lemma apex acute. Palea keels scabrous (finely); puberulous. Apical sterile florets resembling fertile though underdeveloped.

FLOWER Lodicules 2; membranous. Anthers basifixed; 2–4.5 mm long; dehiscent by a longitudinal slit (?); purple.

FRUIT Caryopsis with adherent pericarp. Hilum punctiform.

DISTRIBUTION North America: southwest USA.

NOTES Poeae. Soreng 2005.

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