Flora of North America species comparison

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Eleocharis parvula

Eleocharis sect. Parvulae

dwarf spikerush, dwarf spikesedge, little-head spike-rush, little-head spikesedge, small spike-rush, éléocharide naine
Habit Plants perennial; rhizomes creeping, 0.1–0.2 mm thick, soft, internodes to 4 cm, scales not evident, often terminating in a 2–4 mm tuber with large, acute, terminal bud, or tubers among culm bases.
Culms

terete, 2–9 cm × 0.2–0.5 mm, soft, spongy.
Leaves

distal leaf sheaths often disintegrating, thinly membranous, apex rounded.
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.

basal spikelets absent;

proximal scale empty, amplexicaulous;

floral scales membranous.
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.

anthers 0.6–1.2 mm;

styles 3-fid, rarely some 2-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.

trigonous, rarely some biconvex.
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.

often rudimentary, often narrower than achene summit or sunken in a depression in achene, color and texture either similar to achene summit and tubercle merging with achene, or different and clearly distinct from achene.
2n

= 10 (Europe).

Eleocharis parvula

Eleocharis sect. Parvulae
Phenology Fruiting summer–fall (north) or late winter–fall (far south).
Habitat Brackish or saline, mostly coastal tidal marshes, shores, mud flats, swamps, ponds, ditches
Elevation 0–600 m (0–2000 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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Central America; South America; Temperate to tropical North America; West Indies; Europe; North Africa
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.)

Species 2 (2 in the flora).

Eleocharis sect. Parvulae is usually treated as monotypic. The taxonomy of its species should be carefully studied worldwide. H. K. Svenson (1957) grouped the species of sect. Parvulae with subg. Eleocharis (sect. Eleocharis) ser. Rostellatae and subg. Zinserlingia in E. ser. Pauciflorae (Beauverd) Svenson on the basis of the often poor differentiation between the tubercle and achene. DNA data presented by E. H. Roalson and E. A. Friar (2000) suggest that sect. Parvulae is closely related to 8a1. sect. Eleocharis.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 23, p. 106. FNA vol. 23.
Parent taxa Cyperaceae > Eleocharis > subg. Eleocharis > sect. Parvulae Cyperaceae > 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. 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
Subordinate taxa
Synonyms Scirpus parvulus, E. pygmaea, S. nanus
Name authority (Roemer & Schultes) Link ex Bluff Nees: Comp. Fl. German. ed. 2, 1: 93. (1836) T. V. Egorova: in An. A. Fedorov, Fl. Evr. Chasti SSSR 2: 110. (1976)
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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