14.25 SPHENOPHOLIS Scribn.
Thomas F. Daniel

Plants usually perennial, rarely winter annuals; usually cespitose, sometimes the culms solitary. Culms (5)20–130 cm, leaves evenly distributed. Sheaths open; auricles absent; ligules membranous, erose; blades flat or involute, glabrous or pubescent. Inflorescences panicles, open or contracted, nodding to erect; disarticulation below the glumes, the distal floret sometimes disarticulating first. Spikelets pedicellate, 2.1–9.5 mm, laterally compressed, with 2–3 florets; rachillas glabrous or pubescent, prolonged beyond the base of the distal floret as a slender bristle. Glumes almost equaling the lowest floret, dissimilar in width, membranous to subcoriaceous, margins scarious, apices unawned; lower glumes narrower than the upper glumes, 1(3)-veined, strongly keeled, apices acute; upper glumes elliptical to oblanceolate, obovate, or subcucullate, 3(5)-veined, strongly to slightly keeled, apices acuminate, acute, rounded, or truncate; calluses glabrous; lemmas herbaceous, not indurate, rounded on the lower back, smooth or partly or wholly scabrous, usually keeled near the apices, 3(5)-veined, veins usually not visible, unawned or awned from just below the apices, awns straight or geniculate; paleas hyaline, shorter than the lemmas; lodicules 2, free, membranous, glabrous, toothed or entire; anthers 3; ovaries glabrous. Caryopses shorter than the lemmas, concealed at maturity, linear-ellipsoid, glabrous; endosperm liquid. x = 7. Name from the Greek sphen, ‘wedge’, and pholis, ‘scale’, in reference to the upper glumes.

Sphenopholis includes six species, all of which are native to the Flora region. Its greatest diversity is in the southeastern United States. One species, Sphenopholis obtusata, extends outside the region to southern Mexico and the Caribbean. It has also been collected in Hawaii, but is not known to be established there. Interspecific hybridization is known in the genus, but intermediate plants are not frequently encountered. Trisetum interruptum Buckl. is sometimes treated in Sphenopholis (e.g., Finot et al. 2004) because its spikelets disarticulate below the glumes.

Glume widths are measured in side view, from the lateral margin to the midvein.

SELECTED REFERENCES Erdman, K.S. 1965. Taxonomy of the genus Sphenopholis (Gramineae). Iowa State Coll. J. Sci. 39:289–336; Finot, V.L., P.M. Peterson, R.J. Soreng, and F.O. Zuloaga. 2004. A revision of Trisetum, Peyritscia, and Sphenopholis (Poaceae: Pooideae: Aveninae) in Mexico and Central America. Ann. Missouri Bot. Gard. 91:1–30;Smith, E.B. (ed.). 1991. An Atlas and Annotated List of the Vascular Plants of Arkansas, ed. 2. Edwin B. Smith, Fayetteville, Arkansas, U.S.A. 489 pp.

[Click here for interactive version of dichotomous key, here for multientry interactive key].

1. Distal lemmas awned, awns 3–9 mm long; spikelets 4.5–9.5 mm long S. pensylvanica
1. Distal lemmas unawned or awned, awns 0.1–3 mm long; spikelets 2.1–5.2 mm long (2)
2. Distal lemmas scabrous on the sides, unawned or awned; anthers (0.5)1–2 mm long (3)
2. Distal lemmas usually smooth on the sides, sometimes scabrous or scabridulous distally, unawned; anthers 0.2–1 mm long (4)
3. Lower glumes at least 1/3 as wide as the upper glumes; blades (1)2–5(7) mm wide, flat
to slightly involute; awns absent or shorter than 1 mm S. nitida
3. Lower glumes less than 1/3 as wide as the upper glumes, rarely slightly wider;
blades 0.3–1.5(2) mm wide, involute to filiform; awns absent or (0.1)1–3 mm long S. filiformis
4. Upper glumes subcucullate, the width/length ratio 0.3–0.5; panicles usually erect, often
spikelike, the spikelets usually densely arranged S. obtusata
4. Upper glumes not subcucullate, the width/length ratio 0.17–0.35; panicles usually nodding, not spikelike, the spikelets usually loosely arranged (5)
5. Spikelets 2.1–4 mm long; lowest lemmas 2.1–3 mm long; upper glumes 1.9–2.9 mm
long S. intermedia
5. Spikelets 4–5.2 mm long; lowest lemmas 3.1–4.2 mm long; upper glumes 3–3.9 mm
long S. longiflora

Sphenopholis pensylvanica (L.) Hitchc.
Swamp Oats

Culms 30–120 cm, glabrous. Sheaths glabrous or pubescent; ligules 0.2–1 mm; blades 4–10(20) cm long, (1)2–8 mm wide, flat to slightly involute, smooth or scabridulous, some-times pubescent. Panicles 7–35 cm long, 2–10 cm wide, erect to nodding, with relatively few, loosely arranged spikelets. Spikelets 4.5–9.5 mm. Lower glumes about 1/2 as wide as the upper glumes; upper glumes 3.6–6.2 mm, elliptical to oblanceolate, width/length ratio 0.15–0.28, apices acuminate to acute; lowest lemmas 3.5–6 mm, mostly smooth, apices scabridulous, unawned or awned, awns to 2.5 mm; distal lemmas scabrous, awned, awns 3–9 mm, slightly to evidently bent; anthers 0.5–1.8 mm. 2n = 14.

Sphenopholis pensylvanica grows in springheads, seepage areas, swamps, marshes, and other moist to wet places, at 0–1100 m, in the eastern and southeastern United States. It hybridizes with S. obtusata (see below). The hybrids, which are called Sphenopholis ×pallens (Biehler) Scribn., differ from S. pensylvanica in having generally shorter (3–5 mm) spikelets and shorter (0.1–4 mm), straight or bent awns on the distal lemmas. They differ from S. obtusata in having awns on the distal lemmas.

Sphenopholis nitida (Biehler) Scribn.
Shiny Wedgegrass

Culms 30–80 cm. Sheaths pubescent or the upper sheaths glabrous, sometimes scabrid-ulous; ligules 1–2 mm; blades 2–15 cm long, (1)2–5(7) mm wide, flat to slightly involute, sometimes pubescent, flag leaf blades scabridulous. Panicles 6–20 cm long, 1–5 cm wide, nodding to erect, spikelets loosely to densely arranged. Spikelets 2.5–5 mm. Lower glumes at least 1/3 as wide as the upper glumes; upper glumes 2–3.2 mm, obovate, rarely subcucullate, width/length ratio 0.22–0.38; lowest lemmas 2.1–3.8 mm, smooth on the basal 1/3–1/2, scabrous distally, unawned; distal lemmas scabrous on the sides, usually unawned, rarely awned, awns 0.1–1 mm; anthers (0.5)1–2 mm. 2n = 14.

Sphenopholis nitida grows in moist to dry, deciduous and coniferous forests, on clay or silt banks and slopes, at 0–1200 m, in southern Ontario and the eastern United States. It can be confused with occasional forms of S. obtusata that have somewhat scabrous distal lemmas, but S. nitida has broader lower glumes.

Sphenopholis filiformis (Chapm.) Scribn.
Southern Wedgegrass

Culms 20–100 cm. Sheaths smooth, usually glabrous, some-times pubescent; ligules 0.4–0.75 mm, erose-ciliate; blades 2–45 cm long, 0.3–1.5(2) mm wide, involute to filiform. Panicles 5–15 cm long, 0.5–1(2) cm wide, sometimes nodding, spikelets loosely to densely arranged. Spikelets 2.3–5 mm. Lower glumes less than 1/3 as wide as the upper glumes, rarely slightly wider; upper glumes 1.8–2.9 mm, obovate to oblanceolate, width/length ratio 0.16–0.45, apices rounded to truncate; lowest lemmas 2–3 mm, scabridulous distally; distal lemmas scabrous on the sides, unawned or infrequently awned, awns (0.1)1–3 mm; anthers (0.5)1–1.9 mm. 2n = 14.

Sphenopholis filiformis grows in sandy soils of pine and mixed pine forests, at 0–500 m, in the southeastern United States. It is found primarily in the coastal plain, but extends to the piedmont. Smith (1991) reported it for northern Arkansas (Nielsen 4946, identification not verified). Sphenopholis filiformis differs from occasional forms of S. obtusata with somewhat scabrous distal lemmas in having narrower leaves.

Sphenopholis obtusata (Michx.) Scribn.
Prairie Wedgegrass, Sphenopholis Obtus

Culms (9)20–130 cm. Sheaths glabrous or hairy, sometimes scabridulous; ligules (1)1.5–2.5 mm, erose-ciliate, more or less lacerate; blades 5–14 cm long, (1)2–8 mm wide, usually flat, rarely slightly involute, scab-rous or pubescent. Panicles (2)5–15(25) cm long, 0.5–2 cm wide, usually erect, often spikelike, spikelets usually densely arranged. Spikelets 2.2–3.6 mm. Lower glumes less than 1/3 as wide as the upper glumes; upper glumes 1.5–2.5 mm, subcucullate, width/length ratio 0.3–0.5, apices rounded to truncate; lowest lemmas 1.9–2.8 mm, usually scabridulous distally; distal lemmas usually smooth on the sides, occasionally scabrous, unawned; anthers 0.2–1 mm. 2n = 14.

Sphenopholis obtusata grows in prairies, marshes, dunes, forests, and waste places, at 0–2500 m. Its range extends from British Columbia to New Brunswick, through most of the United States, to southern Mexico and the Caribbean. The distal lemmas of S. obtusata are occasionally somewhat scabrous. Such plants can be distinguished from S. nitida by their narrower lower glumes, from S. filiformis by their wider leaves, and from S. pensylvanica by their shorter, unawned spikelets. Hybrids with S. pensylvanica, called Sphenopholis ×pallens, have short (0.1–4 mm) awns on the distal lemmas.

Sphenopholis intermedia (Rydb.) Rydb.
Slender Wedgegrass, Sphenopholis Intermédiaire

Culms (5)30–120 cm. Sheaths smooth or scabridulous, some-times pubescent; ligules 1.5–2.5 mm, erose-ciliate, often lacer-ate; blades 8–15 cm long, (1)2–6 mm wide, flat to slightly involute. Panicles (2)7–20 cm long, (0.5)1–3 cm wide, usually nodding, not spikelike, spikelets usually loosely arranged. Spikelets 2.1–4 mm. Lower glumes less than 1/3 as wide as the upper glumes; upper glumes 1.9–2.9 mm, oblanceolate to obovate, not subcucullate, width/length ratio 0.23–0.35, apices acute, rounded, or subtruncate; lowest lemmas 2.1–3 mm, smooth or scabridulous; distal lemmas usually smooth on the sides, rarely scabridulous near the apices, unawned; anthers 0.2–0.8 mm. 2n = 14.

Sphenopholis intermedia grows at 0–2500 m in wet to damp sites, sites that dry out after the growing season, and sites with clay soils that retain moisture. Restricted to the Flora region, it is found in forests, meadows, and waste places throughout most of the region other than the high arctic. It differs from Koeleria macrantha, with which it is sometimes confused, in its more open panicles and in having spikelets that disarticulate below the glumes.

Sphenopholis longiflora (Vasey ex L.H. Dewey) Hitchc.
Bayou Wedgegrass

Culms to 70 cm. Sheaths smooth or retrorsely scabrid-ulous, usually glabrous, some-times pubescent; ligules 0.7–2.6 mm, glabrous, erose; blades 8–18 cm long, 2–10 mm wide, flat. Panicles 15–20 cm long, 1.5–2.5 cm wide, nodding, not spikelike, spikelets loosely arranged. Spikelets 4–5.2 mm. Lower glumes about 1/3 as wide as the upper glumes; upper glumes 3–3.9 mm, elliptical to oblanceolate, not subcucullate, width/length ratio 0.17–0.26, apices acute; lowest lemmas 3.1–4.2 mm, glabrous; distal lemmas usually smooth on the sides, rarely scabridulous distally, unawned; anthers 0.2–0.7 mm. 2n = 14.

Sphenopholis longiflora grows in forest bottoms along bayous and streams, from 0–50 m, in Texas, Arkansas, and Louisiana. Erdman (1965) treated both S. longiflora and S. intermedia as S. obtusata var. major (Torr.) Erdman. They are morphologically distinct from each other, and from S. obtusata.