FNA: Eleocharis tricostata

	Eleocharis tricostata
	three-angle spikerush, three-angle spikesedge
Habit	Plants perennial, mat-forming; rhizomes evident, fairly long, 1.5–3 mm thick, hard, cortex persistent, longer internodes 1.5–3 mm, scales disintegrating to fibers, 4–5 mm, papery.
Culms	terete, often with 8–12 blunt ridges when dry, 20–55 cm × 0.3–1.3 mm, soft to hard.
Leaves	distal leaf sheaths persistent, rarely splitting, proximally red to stramineous, distally green to reddish, papery, apex often dark reddish, subtruncate to obtuse, not callose, tooth present on some or all culms of plant, to 0.5 mm.
Spikelets	cylindric to ovoid, 5–20 × 2–3 mm, apex rounded to subacute; proximal scale amplexicaulous, apex entire; subproximal scale empty; floral scales appressed in fruit, 20–200+, 10 per mm of rachilla, dark brown, midrib regions often stramineous or greenish, oblong, 1.7–2.5 × 1 mm, apex entire, broadly rounded, usually recurved, mostly carinate.
Flowers	perianth bristles absent; stamens 3; anthers dark yellow, 1–1.5 mm; styles 3-fid.
Achenes	falling with scales, medium to dark brown, obovoid to obpyriform, with short neck, thickly trigonous, angles prominent (keeled), 0.7–0.9 × 0.4–0.6 mm, obscurely to clearly rugulose at 10–20X with more than 20 horizontal ridges in vertical series and/or minutely cancellate at 20–30X.
Tubercles	brown, rudimentary, mostly apiculate, sometimes pyramidal, 0.05–0.15 × 0.15–0.2 mm.

	Eleocharis tricostata
Phenology	Fruiting late spring–summer.
Habitat	Wet sandy or peaty depressions, pond margins, pine barrens, savannas, mostly coastal plains
Elevation	10–200 m (0–700 ft)
Distribution	AL; FL; GA; MA; MI; NC; NJ; NY; SC; VA [WildflowerSearch map] [BONAP county map]
Discussion	I have not seen specimens to verify reports of Eleocharis tricostata from Louisiana. In the absence of rhizomes and achenes, E. tricostata is easily mistaken for E. montevidensis. (Discussion copyrighted by Flora of North America; reprinted with permission.)
Source	FNA vol. 23, p. 88.
Parent taxa	Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Eleocharis
Sibling taxa	E. acicularis, E. aestuum, E. albida, E. ambigens, E. atropurpurea, E. baldwinii, E. bella, E. bernardina, E. bicolor, E. bifida, E. bolanderi, E. brachycarpa, E. brittonii, E. cancellata, E. cellulosa, E. coloradoensis, E. compressa, E. cylindrica, E. decumbens, E. diandra, E. elliptica, E. elongata, E. engelmannii, E. equisetoides, E. erythropoda, E. fallax, E. flavescens, E. geniculata, E. intermedia, E. interstincta, E. kamtschatica, E. lanceolata, E. macrostachya, E. mamillata, E. melanocarpa, E. microcarpa, E. minima, E. montana, E. montevidensis, E. nana, E. nigrescens, E. nitida, E. obtusa, E. obtusetrigona, E. occulta, E. ovata, E. pachycarpa, E. palustris, E. parishii, E. parvula, E. quadrangulata, E. quinqueflora, E. radicans, E. ravenelii, E. retroflexa, E. reverchonii, E. robbinsii, E. rostellata, E. suksdorfiana, E. tenuis, E. torticulmis, E. tortilis, E. tuberculosa, E. uniglumis, E. vivipara, E. wolfii
Name authority	Torrey: Ann. Lyceum Nat. Hist. New York. 3: 310. (1836)
Web links	Local Web sites: Go Botany, MI Flora WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Eleocharis tricostata

three-angle spikerush, three-angle spikesedge

Habit

Plants perennial, mat-forming; rhizomes evident, fairly long, 1.5–3 mm thick, hard, cortex persistent, longer internodes 1.5–3 mm, scales disintegrating to fibers, 4–5 mm, papery.

Culms

terete, often with 8–12 blunt ridges when dry, 20–55 cm × 0.3–1.3 mm, soft to hard.

Leaves

distal leaf sheaths persistent, rarely splitting, proximally red to stramineous, distally green to reddish, papery, apex often dark reddish, subtruncate to obtuse, not callose, tooth present on some or all culms of plant, to 0.5 mm.

Spikelets

cylindric to ovoid, 5–20 × 2–3 mm, apex rounded to subacute;

proximal scale amplexicaulous, apex entire;

subproximal scale empty;

floral scales appressed in fruit, 20–200+, 10 per mm of rachilla, dark brown, midrib regions often stramineous or greenish, oblong, 1.7–2.5 × 1 mm, apex entire, broadly rounded, usually recurved, mostly carinate.

Flowers

perianth bristles absent;

stamens 3;

anthers dark yellow, 1–1.5 mm;

styles 3-fid.

Achenes

falling with scales, medium to dark brown, obovoid to obpyriform, with short neck, thickly trigonous, angles prominent (keeled), 0.7–0.9 × 0.4–0.6 mm, obscurely to clearly rugulose at 10–20X with more than 20 horizontal ridges in vertical series and/or minutely cancellate at 20–30X.

Tubercles

brown, rudimentary, mostly apiculate, sometimes pyramidal, 0.05–0.15 × 0.15–0.2 mm.

Eleocharis tricostata

Phenology

Fruiting late spring–summer.

Habitat

Wet sandy or peaty depressions, pond margins, pine barrens, savannas, mostly coastal plains

Elevation

10–200 m (0–700 ft)

Distribution

AL; FL; GA; MA; MI; NC; NJ; NY; SC; VA

[WildflowerSearch map]

[BONAP county map]

Discussion

I have not seen specimens to verify reports of Eleocharis tricostata from Louisiana. In the absence of rhizomes and achenes, E. tricostata is easily mistaken for E. montevidensis.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source

FNA vol. 23, p. 88.

Parent taxa

Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Eleocharis

Sibling taxa

E. acicularis, E. aestuum, E. albida, E. ambigens, E. atropurpurea, E. baldwinii, E. bella, E. bernardina, E. bicolor, E. bifida, E. bolanderi, E. brachycarpa, E. brittonii, E. cancellata, E. cellulosa, E. coloradoensis, E. compressa, E. cylindrica, E. decumbens, E. diandra, E. elliptica, E. elongata, E. engelmannii, E. equisetoides, E. erythropoda, E. fallax, E. flavescens, E. geniculata, E. intermedia, E. interstincta, E. kamtschatica, E. lanceolata, E. macrostachya, E. mamillata, E. melanocarpa, E. microcarpa, E. minima, E. montana, E. montevidensis, E. nana, E. nigrescens, E. nitida, E. obtusa, E. obtusetrigona, E. occulta, E. ovata, E. pachycarpa, E. palustris, E. parishii, E. parvula, E. quadrangulata, E. quinqueflora, E. radicans, E. ravenelii, E. retroflexa, E. reverchonii, E. robbinsii, E. rostellata, E. suksdorfiana, E. tenuis, E. torticulmis, E. tortilis, E. tuberculosa, E. uniglumis, E. vivipara, E. wolfii

Name authority

Torrey: Ann. Lyceum Nat. Hist. New York. 3: 310. (1836)

Web links

Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).

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Eleocharis tricostata

Eleocharis tricostata