Eleocharis engelmannii |
Eleocharis tuberculosa |
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Engelman spikerush, Engelmann's spike-rush, Engelmann's spikesedge, englemann's spike-rush |
cone-cup spikerush, long-tubercled spikerush, long-tubercled spikesedge |
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Habit | Plants perennial, forming dense clumps, not stoloniferous. | |
Rhizomes | present or not, caudexlike, ascending, 1 mm thick; internodes and scales hidden by crowded culms, not evident. |
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Culms | 2–40 cm × 0.5–1.5(–2) mm. |
elliptic or sometimes circular, with several rounded ridges and sulcate when dry, 15–75 cm × 0.3(–1.5) mm, firm, minutely granular at 10X. |
Leaves | apex of distal leaf sheath obtuse to acute, tooth to 0.3 mm. |
distal leaf sheaths persistent; stramineous to green, often minutely red-spotted, papery to membranous, apex subacute to narrowly acute, often with tooth-like callus. |
Spikelets | lanceoloid to subcylindric or ovoid, 5–10(–20) × 2–3(–4) mm, apex acute (to rounded); proximal scale empty, encircling ca. 2/3 of culm; floral scales 25–100(–200), 8–12 per mm of rachilla, orangebrown to stramineous, 2(–2.5) × 1–1.3 mm, midribs mostly keeled, ovate, apex narrowly rounded to subacute. |
basal spikelets absent; never proliferous, ovoid, terete, 5–15 × 2.5–4 mm, apex acute; proximal scale empty, deciduous, clasping 1/2 of culm, similar to floral scales; subproximal scale often empty; floral scales spiraled, 10–30, 5–6 per mm of rachilla, pale orange-brown, midribs green, broadly ovate, 2.5–4 × 1.5–2.5 mm, central area and often flanks papery to cartilaginous (or membranous), midrib evident, apex broadly rounded to obtuse. |
Flowers | perianth bristles present or often absent, 5–8, brown, stout, rudimentary to slightly exceeding tubercle; stamens (2–)3; anthers brown to yellow, 0.3–0.7(–1) mm; styles 2–3-fid. |
perianth bristles 5–6, bright brown, stout, slightly shorter than to equaling tubercle; spinules rarely absent, dense, variably from divaricate to antrorse, very short, and blunt to acute, to often much longer and retrorse, sharply acute; stamens 2–3; anthers 0.5–1 mm; styles 3-fid. |
Achenes | 0.9–1.1(–1.5) × 0.7–1.1 mm. |
medium brown, obovoid to obpyriform, compressed (often obscurely) trigonous, angles evident, 0.9–1.7 × 0.8–2 mm; apex often constricted proximal to tubercle, very coarsely cancellate at 10X, each face with 8–10 longitudinal rows of large depressions. |
Tubercles | depressed, subdeltoid, 0.1–0.3(–0.4) × 0.6–0.9(–1) mm, 1/10–2/5 as high as wide, 1/4 or less as high as achene, 9/10 as wide as achene, very rarely 2/5 as high as achene (in E. engelmannii var. robusta). |
bone-white to pale orange-brown, often red-spotted, subpyramidal, cross section plano-convex, 0.9–1.7(–2.4) × 0.7–1.2–2(–2.2) mm, at least as high and wide as achene, spongy, apex rounded, often with an abaxial acute projection. |
2n | = 10. |
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Eleocharis engelmannii |
Eleocharis tuberculosa |
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Phenology | Fruiting spring–fall. | Fruiting spring (in south)–fall. |
Habitat | Fresh shores, marshes, disturbed places | Wet soil, freshwater, ponds, lakeshores, streams, meadows, pine woods, grasslands, disturbed places, bogs |
Elevation | 30–2400 m (100–7900 ft) | 0–500 m (0–1600 ft) |
Distribution |
AL; AR; AZ; CA; CO; CT; DC; DE; IA; ID; IL; IN; KS; KY; MA; MD; MI; MN; MO; MS; MT; ND; NE; NH; NJ; NM; NY; OH; OK; OR; PA; RI; TN; TX; VA; WA; WI; WV; AB; BC; MB; ON
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AL; AR; FL; GA; LA; MA; MS; NC; NJ; SC; TN; TX; NS
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Discussion | Robust plants known only from Missouri and described as Eleocharis engelmannii var. robusta have well-developed caudices, culms to 2 mm wide (pressed), spikelets to 2 cm, floral scales to 2.5 mm and slightly cartilaginous, styles mostly trifid, achenes to 1.5 × 1 mm, and tubercles 0.3–0.5 × 0.7–1 mm and to 2/5 as high as achene. Some specimens are intermediate between E. engelmannii and E. obtusa, or rarely with E. lanceolata. I have not seen specimens to verify literature reports of E. engelmannii from Manitoba, Connecticut, Delaware, Idaho, New Hampshire, North Carolina, Oregon, Rhode Island, South Carolina, South Dakota, or Vermont. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Eleocharis tuberculosa evidently is closely related to E. tortilis, from which it differs in its larger tubercles, culms that are always elliptic in cross section, and perianth bristle spinules that are often divaricate to antrorse and often blunt. The specimens of E. tuberculosa from throughout its range which are like E. tortilis in having retrorsely spinulose perianth bristles have been named E. tuberculosa forma retrorsa Svenson (type from Massachusetts). Plants from Nova Scotia with nearly smooth bristles have been named E. tuberculosa var. pubnicoensis Fernald and E. tuberculosa forma pubnicoensis (Fernald) Svenson. We have not seen voucher specimens for literature reports of Eleocharis tuberculosa from Connecticut, Delaware, Maine, Maryland, New Hampshire, New York, Pennsylvania, Rhode Island, or Virginia. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 104. | FNA vol. 23, p. 92. |
Parent taxa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Ovatae | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Tenuissimae |
Sibling taxa | ||
Synonyms | E. engelmannii var. detonsa, E. engelmannii var. monticola, E. engelmannii var. robusta, E. monticola, E. monticola var. leviseta, E. ovata var. detonsa | Scirpus tuberculosus, E. tuberculosa var. pubnicoensis |
Name authority | Steudel: Syn. Pl. Glumac. 2: 79. (1855) | (Michaux) Roemer & Schultes: in J. J. Roemer et al., Syst. Veg. 2: 152. (1817) |
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