Eleocharis robbinsii |
Eleocharis rostellata |
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Robbin's sppike-rush, Robbins' spikerush, Robbins' spikesedge, éléocharide Robbins |
beak spike-rush, beak spikesedge, walking sedge, walking spikerush |
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Habit | Plants perennial; rhizomes (0.5–)1–2 mm thick, longer internodes 2–3 cm, scales 5–7 mm; tubers sometimes present, apical, ovoid, 4–8 × 3–4 mm. | Plants densely tufted, mat-forming by means of rooting culm tips. |
Culms | acutely trigonous; spikelet-bearing culms 16–70 cm × 0.7–0.9 mm; when submersed plants often forming numerous, filiform, flaccid culms without spikelets, sometimes with whorls of slender branches, 0.1–0.3 mm wide; soft, sometimes septate-nodulose when aquatic, internally spongy, transverse septa incomplete. |
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. |
Leaves | distal leaf sheaths persistent or decaying, membranous, apex obtuse to acuminate. |
distal leaf sheaths not splitting abaxially, proximally dark red to brown, apex usually reddish. |
Spikelets | sometimes proliferous (when submerged), 9–33 × 1.5–3 mm; rachilla joints bearing prominent winglike remnants of floral scales; proximal scale with a flower, amplexicaulous, (5–)6–9.8 mm; floral scales 4–18, 0.5–1 per mm of rachilla, stramineous to pale brown, often minutely dotted reddish, without or rarely with darker submarginal band, narrowly ovate to lanceolate, 5–7.8 × 2–3 mm, thickly papery, membranous toward margins, apex narrowly rounded to acute. |
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. |
Flowers | perianth bristles 6–7, stramineous to reddish brown, proximally slightly flattened, subequal to equal, much exceeding to rarely shorter than achene, 3–5 mm, retrorsely spinulose; anthers yellow to reddish, 1.6–3.2 mm; styles 3-fid. |
perianth bristles brown, equaling achene or tubercle, densely spinulose; anthers brown, 2–2.4 mm. |
Achenes | stramineous or medium brown, biconvex or compressed trigonous, narrowly obpyriform, 1.9–2.6 × 1–1.4 mm, adaxial face with 15–22 rows of rectangular, transversely elongated or nearly isodiametric cells, clearly sculptured at 10–15X, apex usually conspicuously constricted to short neck 0.4–0.7 mm wide, usually wider at tubercle base. |
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. |
Tubercles | stramineous to medium brown, high-pyramidal, 0.5–1.1 × 0.3–0.7 mm. |
when present pale to dark brown, pyramidal, to 0.5 × 0.3 mm. |
Eleocharis robbinsii |
Eleocharis rostellata |
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Phenology | Fruiting late spring–late fall. | Fruiting late spring in south, summer–fall in north. |
Habitat | Shallow waters of fresh lakes and ponds with sandy-peaty soils | Very wet calcareous or brackish fens, springs, shores |
Elevation | 10–500 m (0–1600 ft) | 50–2400 m (200–7900 ft) |
Distribution |
AL; CT; DE; FL; GA; MA; ME; MI; MN; NC; NH; NJ; OH; SC; VA; WI; NB; NS; ON; QC
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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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Discussion | I have not seen voucher specimens for literature reports of Eleocharis robbinsii from Indiana, Pennsylvania, or Rhode Island. Plants from South Carolina with the achene surface cells nearly isodiametric, the achene apex spongy, and the anthers to 3.2 mm may represent an undescribed taxon. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 23, p. 117. | FNA vol. 23, p. 90. |
Parent taxa | Cyperaceae > Eleocharis > subg. Limnochloa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Rostellatae |
Sibling taxa | ||
Synonyms | Scirpus rostellatus | |
Name authority | Oakes: Mag. Hort. Bot. 7: 178. (1841) | (Torrey) Torrey: Fl. New York 2: 347. (1843) |
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