PAPPOSTIPA (Trin. & Rupr.) Romaschenko, P.M. Peterson, and Soreng
Plants perennial; tightly cespitose, sometimes stoloniferous. Culms 10-70 cm tall, basal branching intravaginal; nodes 2-3. Sheaths whitish to reddish brown or purplish; ligules 0.5-3 mm long, lower ligules often densely hairy, sometimes merely ciliate, sometimes glabrous, upper ligules glabrous or sparsely hairy; blades 0.5-2.5 mm wide, convolute, apices pointed; abaxial surfaces sometimes scabrous, usually glabrous, sometimes with hairs; adaxial surfaces hairy. Panicles 3-24 cm long, often partically included in the upper leaf sheath at maturity. Glumes subsequal, 15-45 mm long, longer than the floret, hyaline, with 1-3(5) veins, acuminate. Florets 4-17 mm, fusiform; calluses 1-4 mm; lemmas evenly hairy with hairs 0.5-1 mm long or glabrous on the distal portion of the back, apices not fused into a crown, lobed, lobes to 1 mm. Awns 20-70(195) cm long, persistent, strongly once geniculate; columns 15-33 mm, densly hairy, hairs 4-9 mm long; bristles 12=45(170) mm long; paleas usually subequal to the lemmas, sometimes less than 1/2 as long, usually hairy, sometimes glabrous.
Pappostipa is native to South America and most abundant in Argentina. Romschenko et al. (2008) recognize 14 spcies in the genus of which one, P. speciosa has a disjunct distribution, growing in both South and North America. The genus is readily distinguished by its single florets and sharply once-geniculate awns with their plumose column. The generic description is based on that provided by Romaschenko et al.
Pappostipa speciosa (Trin. & Rupr.) Romaschenko
Plants tightly cespitose, not rhizomatous. Culms 30–60 cm, bases orange-brown; nodes 3–6; basal branching intravaginal. Sheaths mostly glabrous, throats densely ciliate, basal sheaths reddish-brown, flat and ribbonlike with age; ligules varying within a plant, lower ligules 0.3–1 mm, densely hairy and ciliate, hairs 0.2–1 mm, often longer than the basal membrane, upper ligules to 2.5 mm, hyaline to scarious, glabrous or hairy, usually less hairy than the lower ligules, sometimes ciliate; blades 10–30 cm long, 0.5–2 mm wide when flat, usually rolled, to 1 mm in diameter, abaxial surfaces glabrous, smooth, adaxial surfaces pilose. Panicles 10–15 cm, dense, frequently partially included in the upper leaf sheaths at maturity; branches ascending. Spikelets 16–24 mm. Glumes linear-lanceolate, glabrous, tapering from below midlength to the narrowly acute apices; lower glumes 16–24 mm, 1-veined; upper glumes 13–19 mm, 3–5-veined; florets (6)8–10 mm; calluses 0.8–1.6(3) mm, sharp; lemmas densely and evenly hairy, hairs about 0.5 mm, without a pappus; awns 35–45(80) mm, once-geniculate, first segment pilose, hairs 3–8 mm, terminal segment glabrous, smooth; paleas 3.2–5.1 mm, 2/5–2/3(4/5) the length of the lemmas, usually hairy, hairs about 0.5 mm. 2n = 66, 68, about 74.
Pappostipa speciosa grows on rocky slopes in canyons of arid and semiarid regions of the southwestern United States and northern Mexico, and in Chile and northern to central Argentina. Several varieties are recognized in South America. It is not clear to which of these varieties, if any, the North American plants belong.
The reddish-brown leaf bases, differing lower and upper ligules, and the pilose, once-geniculate awns make Pappostipa speciosa an easy species to recognize in North America. It is also an attractive species, well worth cultivating. It prefers open areas with well-drained soils. The growth of young shoots and flowering is stimulated by fire.