Dwarf Spikerush

Nile and Mediterranean regions.

Europe, north Africa, north and central America.

Rice fields.

Perennial.

In Great Britain and/or Ireland:
Foodplant / parasite
embedded sorus of Ustilago marina parasitises live, swollen root of Eleocharis parvula

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.

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. 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. 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. 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. Tubercles 0.1–0.2 × 0.15 mm. 2n = 10 (Europe).

B.C., N.B., Nfld. and Labr., N.S., Que.; Ala., Ark., Calif., Conn., Fla., Ga., Ill., Ind., Kans., La., Maine, Md., Mass., Mich., Miss., Mo., N.J., N.Y., N.C., Ohio, Oreg., S.C., Va., Wash.; Mexico; Central America (Nicaragua); Eurasia.

Fruiting summer–fall (north) or late winter–fall (far south).

Brackish or saline, mostly coastal tidal marshes, shores, mud flats, swamps, ponds, ditches; 0–600m.

Scirpus parvulus Roemer & Schultes in J. J. Roemer et al., Syst. Veg. 2: 124. 1817; Eleocharis pygmaea Torrey; S. nanus Sprengel

Eleocharis parvula (R. & S.) Link; Bluff & Fingerh Compend. Fl. Germ. ed. 2. 1 : 93. 1836.
Scirpus pusillus Vahl, Enum. 2 : 246. 1805. (Based partly on Scirpus capillaceus Michx. which is E. acicularis.) Not Eleocharis pusilla R. Br. 1810.
Scirpus nanus Spreng. Pug. 1 : 4. 1813. (Halle, Germany.) Not S. nanus Poir. 1804; nor Eleocharis nana Kunth, 1837.
Scirpus parvulus R. & S. Syst. Veg. 2: 124. 1817. (Germany.)
Scirpus humilis Wallr. Sched. Crit. 27. 1822. (Germany.) Not S. humilis Veil. 1825; nor 6". humilis Willd. 1837.
Eleogiton parvula Link, Hort. Berol. 1 : 285. 1827.
Limnochloa parvula Reichenb. in Mossier, Handb. ed. 2. 1808. 1829.
Baeothryon nanum A. Dietr. Sp. PI. 2: 91. 1833.
Baeothryon pusillum A. Dietr. Sp. PI. 2 : 92. 1833.
Eleocharis pygmaea Torr. Ann. Lye. N. Y. 3 : 313. 1836. ("Near New York.")
Eleocharis pygmaea 0. ? anachaeta Torr. Ann. Lye. N. Y. 3 : 441. 1836. (New Orleans.)
Scirpus translucens LeGall; J. Lloyd, Fl. Loire-Inf. 275. 1844. (France.) Chaetocyperus pygmaea Walp. Ann. 3: 683. 1852.
> Isolepis leptos SiGxiA. Syn. Cyv91. 1855. (Mexico : Parrj) i JO.)
Chaetocyperus membranaceus Buckl. Proc. Acad. Phila. 1862 : 10. 1862. (Llano County, Texas.)
Eleocharis pusillus Wood, Bot. & Fl. ed. 1871. 361. 1871. Not E. pusilla R. Br. 1810.
Scirpus leptos C. Wright in Sauv. Anal. Acad. Ci. Habana 8 : 80. 1871.
Heleocharis triftora Bock. Flora 63: 437. 1880. (Morro de Boquilla, Vera Cruz: Liebmann.)
Scirpus pollicaris Delile, Descr. Egypte 19: 50 (nomen nudum). 1813. pi. 63, f. 10. 1882. (Egypt.)
Scirpus nanus var. anachaetus Britton, Trans. N. Y. Acad. 11 : 75. 1892.
Cyperus parvulus Missb. & Krause in Sturm, Fl. Deutschl. ed. 2. 2 : 26. 1900.
Scirpus coloradoensis Britton, Torreya 4: 93. 1904. (Larimer County, Colorado.)
Eleocharis leptos Svenson, Rhodora 31 : 176. 1929. Not E. lepta Clarke, 1900.
Eleocharis leptos var. coloradoensis Svenson, Rhodora 31 : 177. 1929.
Eleocharis leptos var. Johnstonii Svenson, Rhodora 31 : 177. 1929. (San Bernadino Mts., California.)
Eleocharis parvula var. anachaeta Svenson, Rhodora 36 : 386. 1934.
Eleocharis parvula f. spongiosa Fassett, Rhodora 39: 273. 1937. (Maine.)
Eleocharis membranacea Gilly, Am. Midi. Nat. 26 : 66. 1941.
Eleocharis coloradoensis Gilly, Am. Midi. Nat. 26: 66. 1941.
Forming mats; roots fibrous, often w^ith minute tuberous stolons; culms capillary (2-7 cm. high), greenish or straw-colored, often spongy and translucent, terete, becoming somewhat striate in drying; upper sheath inconspicuous, membranous; spikelets 2-3.5 mm. long, broadly ovate, 2-9-flowered ; scales ovate, scarcely keeled, obtuse or acute, striate and chartaceous, green to yellowish, often dull brown on the sides ; lowest scale empty, half the length of the spikelet; stamens 3; style trifid; achenes obovate, 1-1.3 mm. long, straw-colored, equilaterally triangular with prominent angles, smooth and shining, under high magnification sometimes lightly striate-reticulate ; style-base very small, triangular, greenish; bristles strawcolored, equaling or exceeding the achene (rudimentary in var. anachaeta, which sometimes has achene angles blunter and the surface more reticulate).
Type locality : Germany ; "in inundatis lacus Koelmensis in Mannsfeldia." Distribution: Saline places in western Europe and along the Mediterranean Sea; Atlantic Coast from Newfoundland to Cuba and Mexico and on the Pacific Coast from Vancouver to California ; inland in New York, Michigan, and Missouri. Var. anachaeta scattered in saline regions from Missouri and westwai^d in the United States and Mexico ; known also from Cuba, and from two collections in South America, at Maracaibo in Venezuela, and Rio de Janeiro.

Eleocharis parvula is a species of spikesedge known by the common names dwarf spikerush, small spikerush and hairgrass in aquaria. It is a plant of brackish and saltwater habitat, such as marshes and mudflats. It is a perennial herb growing tufts of spongy, compressible stems not more than 10 centimeters tall. The plant grows from a tuber which is J-shaped or horseshoe-shaped, a characteristic that helps in the identification of the species. The inflorescence is an oval-shaped spikelet just 2 or 3 millimeters long, made up of several tiny flowers.