Eleocharis engelmannii |
Eleocharis equisetoides |
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Engelman spikerush, Engelmann's spike-rush, Engelmann's spikesedge, englemann's spike-rush |
horsetail spike-rush, horsetail spikesedge, jointed spike-rush, jointed spike-rush (spikesedge), jointed spikesedge, knotted spike-rush |
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Habit | Plants perennial; rhizomes 2–4 mm thick, soft to firm, longer internodes 2–8 cm, scales persistent, 7–8 mm, membranous, tubers absent. | |
Culms | 2–40 cm × 0.5–1.5(–2) mm. |
terete, 50–100 cm × 5–8.4 mm, soft to firm, obscurely to clearly septate-nodulose throughout, internally hollow with complete transverse septa, closer together near the spikelet; plants never forming filiform, flaccid culms. |
Leaves | apex of distal leaf sheath obtuse to acute, tooth to 0.3 mm. |
distal leaf sheaths persistent, membranous to thinly papery, apex acute to slightly acuminate. |
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. |
not proliferous, 20–45 × 4–5(–8) mm; rachilla joints bearing prominent winglike remnants of floral scales; proximal scale empty, amplexicaulous, (2–)2.8–4.9 mm; floral scales 85–160, 1–3 per mm of rachilla, stramineous to pale brown, usually with pale to dark brown submarginal band, obovate to oblong, (4.8–)5.2–7 × 3–4.4 mm, cartilaginous, often membranous toward margins, margins broadly translucent, membranous, apex 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 3–8, stramineous to reddish, slender, vestigial to 2.5 mm, shorter than to equaling achene, smooth or obscurely retrorsely spinulose; anthers stramineous to red-striated, 2.6–3.2 mm; styles 2–3-fid. |
Achenes | 0.9–1.1(–1.5) × 0.7–1.1 mm. |
yellowish to reddish brown, obovoid, biconvex to obscurely compressed trigonous, 1.8–2.3 × 1.4–1.9 mm, obscurely sculptured or sometimes partially smooth at 10–15X, each face with 20–40 rows of linear, transversely elongated cells, lines separating cells obscure, apex with very short neck 0.6–0.8 mm wide. |
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). |
dark brown, lamelliform, high-deltoid, 0.6–1.1 × 0.5–0.7 mm. |
2n | = 10. |
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Eleocharis engelmannii |
Eleocharis equisetoides |
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Phenology | Fruiting spring–fall. | Fruiting late spring–late fall. |
Habitat | Fresh shores, marshes, disturbed places | Fresh ponds, lakes, marshes, streams, ditches, cypress swamps |
Elevation | 30–2400 m (100–7900 ft) | 10–500 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; CA; CT; FL; GA; IN; LA; MA; MD; MI; MO; MS; NC; NY; RI; SC; TX; VA; WI; ON
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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.) |
We have not seen voucher specimens for reports of Eleocharis equistoides from Arkansas and Tennessee. It is probably extirpated from Illinois, Missouri, and Wisconsin. Contrary to previous decriptions, sectioning of the culm reveals that the distance between the septa near the spikelet cannot be used to distinguish the two septate species, E. equisetoides and E. interstincta, which when achenes are absent are better distinguished by the septate-nodulose distal parts of the culms of E. equisetiodes. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 104. | FNA vol. 23. |
Parent taxa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Ovatae | Cyperaceae > Eleocharis > subg. Limnochloa |
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 equisetoides, E. elliottii |
Name authority | Steudel: Syn. Pl. Glumac. 2: 79. (1855) | (Elliott) Torrey: Ann. Lyceum Nat. Hist. New York 3: 296. (1836) |
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