Cyperus schweinitzii |
Cyperus retrofractus |
|
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sand flatsedge, Schweinitz's flatsedge |
rough flatsedge |
|
Habit | Herbs, perennial, rhizomatous. | Herbs, perennial, cespitose. |
Culms | trigonous, (10–)20–50 cm × (0.6–)1–2 mm, glabrous or more often scabridulous, either in distal 1/2 or over entire length; basal sheaths, 1–3, light brown, 1–4 cm, papery. |
with cormlike bases, sharply trigonous, 25–90 cm, glabrous proximally, minutely scabridulous distally. |
Leaves | flat to V-shaped, (2–)20–35 cm × 2–6 mm, margins and keel minutely scabridulous; proximal leaves bladeless. |
V-shaped, 14–40 cm × 3.5–8 mm, (pubescent on adaxial side of midrib). |
Inflorescences | spikes ± umbellate to slenderly (infrequently broadly) ovoid, 10–25 × 7–16 mm; rays 3–5, 1.5–8(–15) cm; bracts 3–7, erect (or declined at most 25–30° from vertical), (2.5–)8–20(–25) cm × (0.5–)1.5–6 mm; rachilla ± deciduous, wingless. |
spikes loose, obtrulloid to obdeltoid (broadest near apex, nearly as long as wide), 20–28(–34) × (12–)15–30 mm; rays 4–13, (1–)4–24 cm (longest ray shorter than bracts), glabrous; bracts 3–12, ascending at 30–45°, flat, 3–25 cm × 3–7 mm; rachilla persistent, wings 0.4–0.6 mm wide, covering 3/4 of mature achene. |
Spikelets | (1–)5–10(–20), oblong to linear-oblong, quadrangular, 7–10(–18) × (2.8–)3.2–4(–4.5) mm; floral scales deciduous, (1–)5–10(–14), spreading, laterally stramineous or dull whitish, sometimes also red-spotted, medially green, laterally 2–3-ribbed, medially 3-ribbed, broadly ovate to oblong-ovate, (2.3–)2.8–3.2 × (2–)2.4–3.2 mm, apex broadly rounded, often clear-erose, cusp 0.1–0.4 mm in proximal scales, 0.3–1 mm in distal scales. |
30–50, proximal one reflexed, distal ones divaricate, linear-lanceoloid, ± terete, (6.5–) 8–10(–17) × 0.5–0.7 mm; floral scales persistent, 3–6(–8), appressed, stramineous (suffused with reddish purple), 4–5-ribbed laterally, ovate-lanceolate, (4–)4.4–4.9(–5.4) × 1.3–1.5 mm; terminal scale not spinose, apex straight, excurved mucronate, or cuspidate. |
Flowers | anthers 0.8–1.4 mm; styles 0.1–0.3 mm; stigmas 1.5–3 mm. |
anthers 0.7–1.2 mm; styles 1.5–2 mm; stigmas 2–2.5 mm. |
Achenes | light to dark brown or nearly black, broadly ellipsoid, infrequently obovoid, 2–2.4 × 0.9–1.4 mm, base cuneate to ± stipelike, apex obtuse to broadly rounded, surfaces papillose. |
brown to brownish black, narrowly oblong, (2.2–)2.5–3 × 0.6–0.7 mm, base cuneate, apex obtuse, apiculate, surfaces puncticulate. |
2n | = 166. |
|
Cyperus schweinitzii |
Cyperus retrofractus |
|
Phenology | Fruiting late spring–early summer. | Fruiting summer. |
Habitat | Riverbanks, sand bars, lakeshores, sand dunes, sandy openings in woods | Roadsides, pastures, disturbed sites in sandy or clayey soils |
Elevation | 0–1000 m (0–3300 ft) | 0–300 m (0–1000 ft) |
Distribution |
CO; IA; IL; KY; MA; MI; MN; MO; MT; NJ; NM; NY; OH; OK; PA; SD; TX; UT; WA; WI; WY; AB; MB; ON; QC; SK; Mexico (Coahuila)
|
AL; AR; DC; DE; GA; KY; MO; NC; NJ; OH; PA; SC; TN; VA
|
Discussion | Cyperus schweinitzii is introduced, but not naturalized, in Massachusetts and Washington. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
For information concerning nomenclature of Cyperus retrofractus, see J. R. Carter and C. E. Jarvis (1986). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 174. | FNA vol. 23, p. 180. |
Parent taxa | Cyperaceae > Cyperus > subg. Cyperus | Cyperaceae > Cyperus > subg. Cyperus |
Sibling taxa | ||
Synonyms | C. alterniflorus | Scirpus retrofractus, C. dipsaciformis, C. retrofractus var. dipsaciformis, Mariscus retrofractus |
Name authority | Torrey: Ann. Lyceum Nat. Hist. New York 3: 276. (1836) | (Linnaeus) Torrey: in J. Carey, Carices North. U.S., 519. (1847) |
Web links |