Flora of North America species comparison

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Eleocharis parvula

Eleocharis diandra

dwarf spikerush, dwarf spikesedge, little-head spike-rush, little-head spikesedge, small spike-rush, éléocharide naine

Wright's spikerush, Wright's spikesedge
Culms

often spreading or reclining, 2–25 cm × 0.3–1 mm.
Leaves

apex of distal leaf sheath acute to acuminate, tooth sometimes present, to 0.2 mm.
Spikelets

2–4 × 1–2 mm, sometimes absent in deeper water;

proximal scale 1/2 or more of spikelet length;

floral scales 6–10 per spikelet, 1.4–2.7 mm, commonly entirely stramineous, apex rounded to subacute.

ovoid, 2–7 × 1–4 mm, apex subacute;

proximal scale either with flower or empty, base encircling 1/2 of culm;

floral scales 50–100, 10 per mm of rachilla, orange to purple-brown, ovate, 1–1.5 × 0.8 mm, midrib slightly keeled, apex rounded to acute.
Flowers

perianth bristles 6, stramineous, fairly stout to slender, usually equaling achene to slightly exceeding tubercle, sometimes unequal and some 1/2 of achene, very rarely rudimentary, minutely retrorsely spinulose;

anthers 0.7–1.2 mm.

perianth bristles absent;

stamens 2(–3);

anthers yellow, 0.2–0.3 mm;

styles 2-fid or some 3-fid.
Achenes

stramineous, sometimes pale brown, obovoid to obpyriform, thickly trigonous, angles distinct, faces concave to plane, rarely convex, 0.9–1.2 × 0.55–0.75 mm, apex tapered, smooth or faintly rough at 30X.

0.7–1 × 0.6–0.9 mm.
Tubers

terminating rhizomes usually markedly J- or horseshoe-shaped, body (apart from apical bud) oblong, 2–2.5(–5) × 0.5–1 mm;

tubers among culm bases straight, narrowly fusiform, 4–5 mm.

Tubercles

0.1–0.2 × 0.15 mm.

deltoid 0.1–0.2 × 0.25–0.45 mm, 1/3–1/2 as high as wide, 1/8–1/4 as high and 3/4–9/10 as wide as achene.
2n

= 10 (Europe).

Eleocharis parvula

Eleocharis diandra
Phenology Fruiting summer–fall (north) or late winter–fall (far south). Fruiting late summer–fall.
Habitat Brackish or saline, mostly coastal tidal marshes, shores, mud flats, swamps, ponds, ditches Fresh, mostly sandy, shores of large lakes and streams, sometimes slightly tidal
Elevation 0–600 m (0–2000 ft) 0–100 m (0–300 ft)
Distribution
from FNA
AL; AR; CA; CT; FL; GA; IL; IN; KS; LA; MA; MD; ME; MI; MO; MS; NC; NJ; NY; OH; OR; SC; VA; WA; BC; NB; NL; NS; QC; Mexico; Central America (Nicaragua); Eurasia
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[BONAP county map]
from FNA
CT; MA; NH; NY; VT; ON
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[BONAP county map]
Discussion

Plants without well-developed bristles are otherwise typical Eleocharis parvula. S.-O. Strandhede and R. M. T. Dahlgren (1968) provided a detailed description from Scandinavia; the mostly curved tubers of North American plants are differently shaped than the ovoid, mostly nearly straight tubers illustrated by them. Eleocharis parvula is very uncommon inland. Plants lacking spikelets and having rather broad culms with evident aerenchyma (E. parvula forma spongiosa Fassett) that are submerged in tidal zones closely resemble small plants of Sagittaria graminea. Eleocharis parvula has also been reported from North Dakota, South America, and Africa; I have not seen specimens. Plants without achenes or tubers cannot be reliably identified to species. Literature reports from Cuba, Mexico, and Venezuela may be based on specimens of E. coloradoensis.

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

Of conservation concern.

Eleocharis diandra is close to E. ovata and E. aestuum; it probably should be treated as a distinct species (A. Haines 2001). It is apparently adapted to the greatly fluctuating water levels of rivers and large lakes (e.g., Oneida Lake in New York, Lake Champlain in Vermont). I have not seen specimens of E. diandra from Maine, New Jersey, or Pennsylvania, which may be based on specimens of E. aestuum. Specimens from the Lake-of-the-Woods shore in southwest Ontario are like E. diandra; they have floral scales with apices rounded, not acute as in typical E. diandra. The only recent observations of E. diandra are from the Connecticut River in Massachusetts (1985) and Oneida Lake in New York (1968; A. Haines 2001).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 23, p. 106. FNA vol. 23, p. 103.
Parent taxa Cyperaceae > Eleocharis > subg. Eleocharis > sect. Parvulae Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Ovatae
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. 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. 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. tricostata, E. tuberculosa, E. uniglumis, E. vivipara, E. wolfii
Synonyms Scirpus parvulus, E. pygmaea, S. nanus
Name authority (Roemer & Schultes) Link ex Bluff Nees: Comp. Fl. German. ed. 2, 1: 93. (1836) C. Wright: Bull. Torrey Bot. Club 10: 101. (1883)
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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