Eleocharis obtusa |
Eleocharis atropurpurea |
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blunt spike-rush, blunt spikesedge, broad spike spikerush, egg-shape spike-rush, éléocharide obtuse |
purple spike-rush |
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Habit | Plants tufted, without creeping rhizomes. | |
Culms | 3–50(–90) cm × 0.2–2 mm. |
2–12(–19) cm × 0.2–0.4 mm. |
Leaves | apex of distal leaf sheath obtuse to acute, tooth to 0.3 mm. |
distal leaf sheaths firm, distally tightly sheathing, apex acute. |
Spikelets | broadly ovoid (to ellipsoid or lanceoloid), apex rounded (to acute), (2–)5–13 × (2–)3–4 mm; floral scales 15–150+, 8–20 per mm of rachilla, orange-brown (to stramineous), elliptic, 1.5–2.5 × 1–1.5 mm, midribs seldom keeled, apex broadly rounded. |
ovoid to ellipsoid, 2–6(–8) × 1–2.5 mm, apex acute; proximal scale with or without flower, not amplexicaulous; floral scales to 100, 15–19 per mm of rachilla, often loosely appressed, dark red-brown to stramineous, ovate to elliptic, 0.6–1.3 × 0.3–0.7 mm, membranous, apex rounded to acute. |
Flowers | perianth bristles (5–)6–7, rarely 0, brown, stout, slightly to usually greatly exceeding tubercle; stamens usually 3; anthers brown to yellow, 0.3–0.6 mm; styles usually 3-fid and 2-fid in same spikelet. |
perianth bristles (0–)4–6, typically 4, colorless to whitish, vestigial to 1/2 as long as achene, smooth or spinuliferous; styles 2-fid. |
Achenes | 0.9–1.2(–1.3) × 0.7–0.9 mm. |
black, obovoid, biconvex, 0.3–0.5 × 0.3–0.4 mm, apex often constricted proximal to tubercle, smooth at 40X. |
Tubercles | deltoid 0.35–0.5 × (0.4–)0.5–0.8 mm, 1/3–2/3 as high as wide, 1/3–1/2 as high and 2/3–9/10 as wide as achene. |
stramineous to whitish, umbonate to subconic, 0.1–0.2 × 0.1–0.2 mm, apex acute. |
2n | = 10. |
= 20. |
Eleocharis obtusa |
Eleocharis atropurpurea |
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Phenology | Fruiting summer–fall. | Fruiting summer–fall (Jun–Sep). |
Habitat | Fresh shores, marshes, disturbed places | Canal banks, hammocks, irrigation ditches, lake and pond margins, maritime shores, rice fields |
Elevation | 10–1600 m [30–5200 ft] | 0–1800 m [0–5900 ft] |
Distribution |
AL; AR; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; ME; MI; MN; MO; MS; NC; NE; NH; NJ; NY; OH; OK; OR; PA; RI; SC; TN; TX; VA; VT; WA; WI; WV; WY; HI; BC; NS; ON; PE; QC
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AL; CA; FL; GA; IA; KS; LA; MI; MO; NC; NE; NM; OK; SC; TX; WA; BC; Mexico; Central America; South America; West Indies; Europe (naturalized); Asia; Africa; Pacific Islands
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Discussion | Extremely uncommon plants of Eleocharis obtusa without perianth bristles may be called E. obtusa var. peasei (type from New Hampshire). Robust plants with distinct caudices, floral scales 2.5 mm, and achenes 1.2–1.3 mm (Eleocharis obtusa var. gigantea Fernald) are rare (specimens seen from the Washington-British Columbia border [type], Arkansas, and the Hawaiian Islands). Dwarf plants (E. obtusa var. jejuna Fernald, type from Maine), with unusually small achenes and floral scales, and tubercles often less than 0.5 mm wide, are occasional in the East and are easily confused with E. ovata and E. aestuum. A few specimens are intermediate with E. engelmannii. Eleocharis obtusa is sometimes treated as conspecific with E. ovata, which consistently differs in its mostly 2-fid styles, mostly two stamens, and especially its narrower tubercles (B. M. H. Larson and P. M. Catling 1996). Eleocharis macounii Fernald has been treated as a synonym of E. obutsa (H. K. Svenson 1957) but is more probably a hybrid between E. intermedia and E. obtusa (P. M. Catling and S. G. Hay 1993; see 34. E. intermedia). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Eleocharis atropurpurea has been reported from Colorado, Montana, and Virginia; I have not seen voucher specimens. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 105. | FNA vol. 23, p. 102. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Scirpus obtusus, E. obtusa var. ellipsoidales, E. obtusa var. gigantea, E. obtusa var. jejuna, E. obtusa var. peasei | Scirpus atropurpureus |
Name authority | (Willdenow) Schultes: Mant. 2: 89. (1824) | (Retzius) J. Presl & C. Presl: in C. B. Presl, Reliq. Haenk. 1: 196. (1828) |
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