14.42 PODAGROSTIS (Griseb.) Scribn. & Merr.
M.J. Harvey and Mary E. Barkworth

Plants perennial; cespitose, sometimes also rhizomatous. Culms 5–90 cm, erect or decumbent at the base. Leaves basally concentrated; sheaths open to the base, smooth, glabrous; auricles absent; ligules memb, scabridulous dorsally, truncate to subacute, entire to lacerate; blades flat, folded or involute. Inflorescences panicles, exserted at maturity, not disarticulating; branches ascending to erect or appressed. Spikelets pedicellate, weakly laterally compressed, with 1 floret; rachilla usually prolonged 0.1–1.9 mm beyond the base of the floret, sometimes absent, especially from the lower spikelts within a panicle, apices glabrous or with hairs, hairs to 0.3 mm; disarticulation above the glums, beneath the floret. Glumes equal or the lower glume longer than the upper, flexible, acute to acuminate, soometimes apiculate, unawned; calluses glabrous or hairy, hairs to 0.5 mm; lemmas membranous, (3)5-veined, veins mostly obscure, somtimes prominent distally, apices truncate to rounded or acute, unawned or awned, awns to about 1.3 mm, usually subapical, occasionally attached near midlength; paleas more than 1/2 as long as the lemmas, 2-veined, thinner than the lemmas; anthers 3. Caryopses shorter than the lemmas, concealed at maturity. x = 7. Name from the Greek pous, ‘foot’, and the genus Agrostis.

Podagrostis is a genus of six or more species that grow in cool, wet areas. In the past, its species have been included in Agrostis. Three species grow in North America north of Mexico. Podagrostis differs from Agrostis in its combination of a relatively long palea and, usually, the prolongation of the rachilla beyond the base of the floret. It differs from Calamagrostis in the poorly developed callus hairs and awns. This treatment differs from the treatment in the FNA volumes and the Manual in recognizing P. thurberiana as distinct from P. humilis, a decision based on consideration of Arnow (1987) and additional examination of specimens.

1. Glumes 2.3-4.3 mm long; rachilla prolongations 0.5-1.9 mm long ..... P. aequivalvis
1. Glumes 1.6-2.5 mm long; rachilla prolongations 0.1-0.6 mm long (2)
2. Glumes ovate to elliptic, exceeding the lemma by 0.2–0.4 mm; panicles 1.5–6 cm long; leaf blades 0.4–1.5 mm wide, highest lead blade usually below mid-culm .....P. humilis
2. Glumes narrowly elliptic, equalling the lemma or up to 0.1 mm long; panicles (2.5)5–12 cm long; leaf blades 1–3 mm wide, highest leaf blade usually about mid-culm .....P._thurberiana

Podagrostis aequivalvis (Trin.) Scribn. & Merr.
Arctic Bent

Plants rhizomatous. Culms 25-90 cm tall, erect; nodes 2-4(6). Ligules 0.4-4 mm, truncate to subacute, entire or lacerate; blades 4-18 cm long, 1-2.5 mm wide, flat. Panicles 5-15 cm long, 2-10 cm wide, lanceloid to ovoid, often drooping, sparsely branched;lowest node with 1-(5) branches; branches usually scabridulous, sometimes smooth, erect to ascending or spreading, spikelets usually restricted to the distal 1/2; lower branches 3-6 cm; pedicels 2-10 mm. Spikelets usually purplish bronse, sometimes greenish purple; rachilla prolongations 0.5-1.9 mm, bristelike, distal hairs shorter than 0.3 mm. Glumes usually subequal, 2.3-4.3 mm, veins sparsely scabridulous distally, apices acute to acuminate, sometimes apiculate; lower glumes usually 3-veined, lateral veins faint; calluses glabrous or sparsely hairy, hairs to 0.1 mm long; lemmas 2.5-3.5 mm long, smooth, opaque, 3(5)-veined, veins usually obscure, apices acute, entire or the veins excurrent to about 0.3 mm, unawned; paleas 2-3 mm,; anthers 3, 0.8-1.3 mm. Caryopses 1.2-1.5 mm; endosperm solid. 2n = 14.

Podagrostis awquivalvis grows along lake, bog, and stream margins, and in forest fens. it is common in the coastal regions of Alaska and British Columbia, and occurs less frequently inland, as well as to about 1500 m in the Cascade Mountains south to Oregon.

Podagrostis humilis (Vasey) Björkman
Alpine Bent
Plants cespitose, sometimes rhizomatous. Culms 3–26 cm, erect to ascending; nodes 2–3. Ligules (0.2)0.5–4 mm, smooth, truncate, rounded or acute, usually entire or erose; blades 1.5–4(5) cm long, 0.4–1.5 mm wide, flat or folded; flag blades usually below, sometimes near midculm. Panicles 1.5–6 cm long, 0.2–0.7(1.5) cm wide, sometimes wider at anthesis, linear to narrowly oblong, lowest node with 1–3(4) branches; branches smooth, usually appressed to erect, ascending at anthesis, branching in the distal 1/3–3/4; lower branches 0.5–1.5 cm; pedicels 0.4–1.5 mm. Spikelets usually purplish; rachilla prolongations 0.1–0.6 mm, glabrous or bristlelike, with a tuft of short hairs at the apex. Glumes subequal, 1.6–2 mm, exceeding the lemma by 0.2–0.4 mm, ovate to elliptical, 1-veined or 3-veined at base, veins smooth or scabridulous distally, apices acute; calluses glabrous or sparsely hairy, hairs to 0.5 mm; lemmas 1.5–2 mm, usually purplish, smooth, opaque, 5-veined, veins obscure or prominent distally, apices acute, entire or erose, rarely awned, awns to about 1.3 mm, usu subapical, smt attached near midlength, lemma veins occasionally excurrent to 0.4 mm; paleas 0.9–1.6 mm; anthers 3, 0.4–1mm. Caryopses 1–1.3 mm. 2n = 14.

Podagrostis humilis is a western North American species that grows in undisturbed alpine and subalpine meadows and screes at over 3500 m, down to meadows, fens, and open woodlands at less than 200 m. It usually differs from P. thurberiana in overall size and in having narrower, more basally concentrated leaves. In the field, dwarf forms of P. humilis mimic Agrostis variabilis; they differ from that species in having paleas.

Podagrostis thurberiana(Hitchc.) Hulten
Thurbers’s Bent

Plants cespitose, sometimes rhizomatous. Culms 10–40(50) cm, ascending, bases sometimes somewhat decumbent; nodes 2–4. Ligules (0.2)0.5–2 mm, smooth, truncate to rounded, entire or erose; blades 3–10(15) cm long, 1–3 mm wide, usually flat, sometimes folded; flag blade usually near midculm. Panicles (2.5)5–12 cm long, 0.5–0.7(2.5) cm wide, linear to narrowly oblong, lowest node with 1–3(4) br; branches scabridulous or smooth, erect to ascending, branching in the distal 1/2–2/3; lower branches 0.5–2.5 cm; pedicels 0.5–2 mm. Spikelets usually greenish, sometimes purplish; rachilla prolongations 0.1–0.6 mm, glabrous or bristlelike, with a tuft of short hairs at the apex. Glumes subequal, 2–2.5 mm, from equalling the lemma to exceeding it by 0.1 mm, elliptic, 1–3-veined, veins smooth or scabridulous distally, apices acute; calluses glabrous; lemmas 2–2.5 mm, greenish or partly purplish, smooth, opaque, 5-veined, veins obscure or prominent distally, apices acute, entire or erose, usually unawned, rarely awned, awns to about 1.3 mm, usually subapical, sometimes attached near midlength, veins occasionally excurrent to 0.4 mm; paleas 1.2–1.6 mm; anthers 3, 0.4–0.8 mm. Caryopses 1–1.3 mm. 2n = 14.

Podagrostis thurberiana is a western North American species that grows in undisturbed alpine and subalpine meadows and screes at over 3500 m, down to meadows, fens, and open woodlands at less than 200 m, sometimes growing with P. humilis. It usually differs from that species in being taller in having wider, less basally concentrated leaves.