Eleocharis rostellata |
Eleocharis diandra |
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beak spike-rush, beak spikesedge, walking sedge, walking spikerush |
Wright's spikerush, Wright's spikesedge |
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Habit | Plants densely tufted, mat-forming by means of rooting culm tips. | |
Culms | 1.5–3 times as wide as thick, 20–100 cm × 0.35–2 mm, firm to hard, wiry, with to 8 subacute ribs, rarely nearly smooth; some culms arching or decumbent and rooting at tips. |
often spreading or reclining, 2–25 cm × 0.3–1 mm. |
Leaves | distal leaf sheaths not splitting abaxially, proximally dark red to brown, apex usually reddish. |
apex of distal leaf sheath acute to acuminate, tooth sometimes present, to 0.2 mm. |
Spikelets | ovoid, 5–17 × 2.5–5 mm, apex acute; spikelets on stolons rudimentary, non-flowering, proliferous when rooting; proximal scale empty, amplexicaulous, ovate, 2–4 mm; subproximal scale with flower; floral scales 20–40, 2–3 per mm of rachilla, stramineous to medium brown, midrib region paler, ovate, 3.5–6 × 2–3 mm, membranous to cartilaginous, apex entire, rounded to subacute. |
ovoid, 2–7 × 1–4 mm, apex subacute; proximal scale either with flower or empty, base encircling 1/2 of culm; floral scales 50–100, 10 per mm of rachilla, orange to purple-brown, ovate, 1–1.5 × 0.8 mm, midrib slightly keeled, apex rounded to acute. |
Flowers | perianth bristles brown, equaling achene or tubercle, densely spinulose; anthers brown, 2–2.4 mm. |
perianth bristles absent; stamens 2(–3); anthers yellow, 0.2–0.3 mm; styles 2-fid or some 3-fid. |
Achenes | often very variable within one plant, ovoid to obovoid or obpyriform, 1.5–2.5 × 1–1.2 mm, beak to 1 × 0.6 mm. |
0.7–1 × 0.6–0.9 mm. |
Tubercles | when present pale to dark brown, pyramidal, to 0.5 × 0.3 mm. |
deltoid 0.1–0.2 × 0.25–0.45 mm, 1/3–1/2 as high as wide, 1/8–1/4 as high and 3/4–9/10 as wide as achene. |
Eleocharis rostellata |
Eleocharis diandra |
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Phenology | Fruiting late spring in south, summer–fall in north. | Fruiting late summer–fall. |
Habitat | Very wet calcareous or brackish fens, springs, shores | Fresh, mostly sandy, shores of large lakes and streams, sometimes slightly tidal |
Elevation | 50–2400 m (200–7900 ft) | 0–100 m (0–300 ft) |
Distribution |
AZ; CA; CT; DE; FL; ID; IL; IN; KS; LA; MA; MD; ME; MI; MN; MT; NC; NE; NJ; NM; NV; NY; OH; OK; PA; RI; SC; SD; TX; UT; VA; WA; WI; WY; BC; NS; ON; Mexico; West Indies (Cuba, Haiti, Puerto Rico)
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CT; MA; NH; NY; VT; ON
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Discussion | Eleocharis rostellata is highly competitive, often forming large monospecific colonies. The South American E. platypus C. B. Clarke is often treated as a synonym of E. rostellata. Eleocharis rostellata superfically closely resembles E. suksdorfiana in its culms, spikelets, and achenes, but differs in the absence of creeping rhizomes, presence of stoloniferous culms, absence of a flower in the proximal scale, and achene surface details. The collection of E. rostellata I have seen from Miami-Dade County, Florida, is from 1877. I have not seen vouchers for Archuleta County, Colorado, by H. D. Harrington (1954), or for the localities in Montana and South Carolina, which are based on the map in H. K. Svenson (1934). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. Eleocharis diandra is close to E. ovata and E. aestuum; it probably should be treated as a distinct species (A. Haines 2001). It is apparently adapted to the greatly fluctuating water levels of rivers and large lakes (e.g., Oneida Lake in New York, Lake Champlain in Vermont). I have not seen specimens of E. diandra from Maine, New Jersey, or Pennsylvania, which may be based on specimens of E. aestuum. Specimens from the Lake-of-the-Woods shore in southwest Ontario are like E. diandra; they have floral scales with apices rounded, not acute as in typical E. diandra. The only recent observations of E. diandra are from the Connecticut River in Massachusetts (1985) and Oneida Lake in New York (1968; A. Haines 2001). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 90. | FNA vol. 23, p. 103. |
Parent taxa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Rostellatae | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Ovatae |
Sibling taxa | ||
Synonyms | Scirpus rostellatus | |
Name authority | (Torrey) Torrey: Fl. New York 2: 347. (1843) | C. Wright: Bull. Torrey Bot. Club 10: 101. (1883) |
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