POACEAE

GRASS FAMILY

James P. Smith, Jr., except as specified

Annual to bamboo-like; roots generally fibrous
Stem generally round, hollow; nodes swollen, solid
Leaves alternate, 2-ranked, generally linear; sheath generally open; ligule membranous or hairy, at blade base
Inflorescence various (of generally many spikelets)
Spikelet: glumes generally 2; florets (lemma, palea, flower) 1–many; lemma generally membranous, sometimes glume-like; palea generally ± transparent, ± enclosed by lemma
Flower generally bisexual, minute; stamens generally 3; stigmas generally 2, generally plumose
Fruit: achene-like grain
Genera in family: 650–900 genera; ± 10,000 species: worldwide; greatest economic importance of any family (wheat, rice, maize, millet, sorghum, sugar cane, forage crops, ornamental, weeds; thatching, weaving, building materials)
Reference: [Hitchcock 1951 Manual grasses US, USDA Misc Publ 200; Clayton & Renvoise 1986 Kew Bull Add Series 13]
See Glossary p. 26 for illustrations of general family characteristics. Generally wind-pollinated.

POA

BLUEGRASS

Robert J. Soreng

Annual, perennial herb, some ± dioecious
Stem 0.3–12 dm
Leaf: sheath open to closed (best observed on upper stem leaf); ligule thin, flexible; blade grooved above on both sides of midvein, flat, folded, or inrolled, generally smooth or scabrous on veins, generally prow-tipped
Inflorescence panicle-like; branches appressed to drooping
Spikelet generally compressed, breaking between florets; glumes 2, similar, generally < lowest lemma, awnless; florets generally 2–6; callus indistinct, often with obvious tuft of long cobwebby hairs; lemma generally keeled to base, of same texture as glumes, awnless, veins generally 5, ± converging near tip; palea well developed, keels generally scabrous; fertile anthers 0.2–4.5 mm; ovary glabrous
Species in genus: ± 500 species: temp and cool regions
Etymology: (Greek: ancient name)
Reference: [Soreng 1991 Syst Bot 16:507–528]
CA is center of diversity in North America. Spikelet features best observed on lowest florets of spikelet.

Native

P. stebbinsii Soreng

Perennial, cespitose, generally 1–3.5 dm, slender, ± dioecious
Leaf: sheath open 3/5–4/5 length; ligule of uppermost leaf of sterile stem 2.5–6 mm, clear, smooth; blade ± firm, folded, inrolled, upper blade surface on sterile stems ± finely hairy
Inflorescence 3–7 cm, narrowly lanceolate, dense to sparse and interrupted
Spikelet: callus glabrous; lemma 3.7–5.5 mm, glabrous, smooth or barely scabrous, thin
Flower bisexual or pistillate (rarely staminate); fertile anthers 2–4.5 mm
Chromosomes: 2n=42,81
Ecology: Subalpine to lower alpine meadows
Elevation: 2700–3700 m.
Bioregional distribution: c&s High Sierra Nevada.Formerly mistaken for P. hansenii Scribner or P. leibergii Scribner. Hybridizes with P. keckii, P. secunda subsp. s.
Flowering time: Summer
.