10.07 STIPA L.
Mary E. Barkworth
Plants annual or perennial; tufted or cespitose, not rhizomatous. Culms 10–200 cm, herbaceous, not branching at the upper nodes; basal branching usually intravaginal; prophylls shorter than the sheaths. Leaves mostly basal; cleistogenes usually not developed; sheaths open; auricles absent; ligules membranous, sometimes stiffly so, upper and lower ligules similar or upper ligules longer than those below; blades prominently ribbed, usually tightly convolute when dry. Inflorescences terminal panicles, usually contracted. Spikelets 12–90 mm, with 1 floret; rachillas not prolonged beyond the base of the floret; disarticulation above the glumes, beneath the floret. Glumes much longer than the floret, hyaline to membranous, usually acuminate, 1–3-veined; florets 3–27 mm, terete to slightly laterally compressed; calluses (1)1.5–6 mm, sharp or blunt, antrorsely hairy; lemmas coriaceous to indurate, tan to brown, smooth, glabrous or hairy, hairs sometimes uniformly distributed, sometimes in lines, margins flat, slightly overlapping at maturity, apices awned, lemma-awn junction evident; awns 50–500 mm, persistent, usually once- or twice-geniculate, sometimes plumose in whole or in part, basal segment often strongly twisted; paleas from shorter than to subequal to the lemmas, glabrous, 2-veined, not keeled, flat between the veins, apices sometimes scarious, sometimes similar in texture to the body; lodicules 2 or 3, glabrous or pilose; anthers 3; styles 2(3,4), free at the base, if 3 or 4, then 1 or 2 distinctly shorter. Caryopses fusiform, not ribbed. x = 11. Name from the Latin stipa, ‘oakum’ (a loose bunch of fibers), alluding both to the feathery inflorescences and the use of Stipa tenacissima L. [ = Macrochloa tenacissima] as a source of cordage.
As treated here, Stipa is a genus of 150–200 species, all of which are native to Eurasia or northern Africa. Until recently, the genus was interpreted as including almost all species of Stipeae with cylindrical florets. In several parts of the world, this broader interpretation still prevails. Jacobs et al. (2006) found that even the European members of Stipa included in their study appeared to be polyphyletic. The most appropriate circumscription of the genus, and its size, is difficult to determine in the absence of a study that encompasses the Eurasian and North African members of the tribe.
Two species of Stipa grow in the Flora region. Stipa pulcherrima is cultivated as an ornamental; Stipa capensis has been introduced, probably accidentally.
SELECTED REFERENCES Freitag, H. 1985. The genus Stipa in southwest and south Asia. Notes Roy. Bot. Gard. Edinburgh 42:355–487; Jacobs, S.W.L., R. Bayer, J. Everett, M.O. Arriaga, M.E. Barkworth, A. Sabin-Badereau, M.A. Torres, F. Vázquez, and N. Bagnall. 2006. Systematics of the tribe Stipeae using molecular data. Aliso 23:349–361.
For an interactive dichotomous key, click here; the interactive, multientry key is not yet available.
1. Plants perennial; glumes 60–90 mm long; awns plumose on the distal segment, hairs 5–6 mm long ... S. pulcherrima
1. Plants annual; glumes 12–20 mm long; awns glabrous on the distal segment ... S. capensis
1. Stipa pulcherrima K. Koch
Plants perennial; cespitose, not rhizomatous. Culms 40–100 cm, glabrous or pubescent below the panicles. Sheaths longer than the internodes, smooth, mostly glabrous, margins sometimes ciliate; ligules 0.5–2 mm on the innovations, to 9 mm on the cauline leaves, stiffly membranous, pubescent, entire to erose; blades 2–5 mm wide when flat, 0.3–0.9(1.5) mm in diameter if involute, abaxial surfaces glabrous, smooth or scabrous, adaxial surfaces glabrous, scabrous, or hirsute, hairs to 0.6 mm. Panicles 10–15 cm, contracted, usually partially enclosed in the upper sheath; branches appressed to ascending, with 1–4 spikelets. Glumes 60–80(90) mm, long-attenuate, mostly hyaline; florets (18)20–27 mm; calluses 3–6 mm; lemmas with lines of hair over the veins and marginal veins, lines over the marginal veins longest, extending to the lemma apices; awns (250)300–500 mm, twice-geniculate, first 2 segments glabrous or hairy, hairs to 2 mm, terminal segment plumose, hairs 5–6 mm, spreading; paleas subequal to the lemmas, usually hairy on the keels, apices scarious; anthers 5–10 mm, not penicillate, yellowish or purplish; styles 2. Caryopses 10–18 mm. 2n = 44.
Stipa pulcherrima is native from France and Germany to Armenia, Azerbaijan, Turkey, and Iran. Freitag (1985) regarded it as a subspecies of S. pennata L. Its long, plumose awns make it a striking ornamental.
2. Stipa capensis Thunb.
Plants annual, tufted. Culms 10–100 cm, erect or geniculate, glabrous, sometimes branching from the lowermost nodes. Sheaths glabrous or pilose; collars with tufts of hair at the sides; ligules 0.4–0.7 mm, membranous, ciliate; blades to 3 mm wide, flat or convolute, abaxial surfaces glabrous, sparsely pubescent, or pilose, adaxial surfaces scabrous or hairy, hairs about 0.8 mm. Panicles 3–15 cm, contracted, often partially enclosed in the upper sheath; branches scabrous; pedicels shorter than the spikelets. Glumes 12–20 mm, narrowly lanceolate to linear, 3-veined, tapering to the hairlike apices; lower glumes equal to or exceeding the upper glumes; florets 4–7 mm, terete; calluses 1.7–2.3 mm, sharp; lemmas indurate, with overlapping margins, dorsally constricted below the apices; awns 50–100 mm, twice-geniculate, first 2 segments twisted and pilose, hairs about 1 mm, terminal segment straight, glabrous; paleas 1.2–1.5 mm, 2-veined, glabrous; lodicules 2; anthers 3, 2–2.5 mm. 2n = 36.
Stipa capensis is known from two locations in Riverside County, California: one in Palm Springs, and the other near the mouth of Chino Canyon. A.C. Sanders (University of California, Riverside) described the latter population as a “common annual on roadside and spreading into desert vegetation” (UTC 230476).