Flora of North America species comparison

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Eleocharis pachycarpa

Eleocharis radicans

black sand spikerush, broad fruit spikerush

creeping spikerush, radical fiber optic spikerush, root spikerush
Habit Plants perennial, forming dense clumps, often stoloniferous. Plants perennial, mat-forming; rhizomes 0.2–0.5 mm thick, longer internodes 5–10 mm, scales not evident.
Rhizomes

present, caudexlike, mostly concealed by crowded culms, vertical or ascending, 2 mm thick;

internodes very short, scales disintegrating to fibers, 4 mm, papery.

Culms

erect to ascending or arching, acutely quadrangular, deeply sulcate, 7–50 cm × 0.3–0.5 mm, smooth, firm.

obscurely to ca. 10-ribbed when dry, terete, 1–12 cm × 0.4–1 mm, very soft, spongy.
Leaves

distal leaf sheaths persistent, proximally brown or reddish, distally stramineous to green, thickly membranous, apex acute or subacute.

distal leaf sheaths fugaceous, colorless, translucent, apex blunt.
Spikelets

basal spikelets absent; often proliferous, ovoid, terete, 3–10 × 2–3 mm, apex acute;

proximal scale empty, amplexicaulous, similar to floral scales;

subproximal scale with a flower;

floral scales spiraled, 8–15, 4 per mm of rachilla, orange-brown, midrib region broadly stramineous or like flanks, ovate, 2–3 × 1.2–2 mm, membranous, midrib evident to prominent, apex acute (to rounded).

ovoid, 2–3 × 1–1.5 mm, apex acute;

scales 5–15, 5–7 per mm of rachilla, colorless to stramineous, rarely slightly reddish, medially broadly greenish to colorless, faintly 3–5-veined, often ovate, membranous, fleshy;

proximal scale 2–2.5 × 0.7 mm, other scales 1.5–2 × 0.7 mm, midrib obscure to slightly keeled, apex acute to rounded.
Flowers

perianth bristles 6 or fewer, stramineous, unequal, some or most equaling achene, spinules obscure, sparse, retrorse, sharply acute.

perianth bristles equaling achene;

anthers yellow to brown, 0.3–0.5 mm.
Stamens

3;

anthers 1.2–1.5 mm.

Styles

3-fid.

Achenes

stramineous, broadly obpyriform, equilaterally trigonous, angles evident, blunt, 0.9–1.1 × 0.7–0.9 mm, apex nearly truncate, smooth or obscurely papillose or rugulose at 20X.

brownish, angles plus longitudinal ridges ca. 7, narrowly obovoid, 2 times longer than wide, 0.75–0.9 × 0.35–0.4 mm, trabeculae ca. 50, distinct.
Tubercles

stramineous, pyramidal, trigonous, usually acute, proximally trilobed, the lobes decurrent on achene, 0.5–0.9 × 0.7–0.9 mm.

brown, pyramidal, 0.15 × 0.15–0.2 mm.

Eleocharis pachycarpa

Eleocharis radicans
Phenology Fruiting late spring–summer. Fruiting spring–winter (Apr–Dec).
Habitat Fresh shores, streambeds, groundwater seeps Stream alluvium, lake margins, meadows, seeps, bogs
Elevation 100–1400 m (300–4600 ft) 100–1400 Ariz., Calif., Fla., La., Mich., Okla., Tex., Va.
Distribution
from FNA
CA; NV; South America (Argentina, Chile) [Introduced in North America; introduced in Australia]
[WildflowerSearch map]
[BONAP county map]
from FNA
HI; n Mexico; West Indies; Central America (El Salvador); South America (Argentina, Chile)
[WildflowerSearch map]
[BONAP county map]
Discussion

H. K. Svenson (1957) placed Eleocharis pachycarpa in ser. Sulcatae Svenson. Contrary to his statement that perianth bristles are often lacking, they are present in all of the specimens we have seen. Superficially similar to E. bolanderi, from which it may readily be distinguished by its oblique leaf sheath summits, 4-angled culms, pyramidal tubercles, and often proliferating spikelets. The earliest North American specimen we have seen was collected in 1919 in Tuolumne County, California.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 23, p. 91. FNA vol. 23, p. 112.
Parent taxa Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Tenuissimae Cyperaceae > Eleocharis > subg. Scirpidium
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. 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. tricostata, E. tuberculosa, E. uniglumis, E. vivipara, E. wolfii
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. ravenelii, E. retroflexa, E. reverchonii, E. robbinsii, E. rostellata, E. suksdorfiana, E. tenuis, E. torticulmis, E. tortilis, E. tricostata, E. tuberculosa, E. uniglumis, E. vivipara, E. wolfii
Synonyms Scirpus radicans, E. acicularis var. radicans, E. lindheimeri
Name authority E. Desvaux: in C. Gay, Fl. Chil. 6: 174. (1853) (Poiret) Kunth: Enum. Pl. 2: 142. (1837)
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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