Eleocharis microcarpa
Eleocharis coloradoensis
small-fruit spikesedge, smallfruit spikerush
dwarf spike-rush
often ascending or arching, quadrangular or broadly elliptic, 2–40 cm × 0.1–0.4(–0.6) mm, soft.
distal leaf sheaths persistent or disintegrating, pale brown, green or red-brown, streaked or mottled red-brown or purple, translucent, membranous, apex narrowly acute.
basal spikelets absent; often proliferous, ovoid to ellipsoid or lanceoloid, terete, 2–10.7 × 1–2 mm, apex acute;
proximal scale empty, persistent, amplexicaulous, dissimilar to floral scales, often longer, often resembling an involucral bract, ovate to lanceolate, midrib markedly thickened and broad and often prolonged beyond lamina;
subproximal scale with flower;
floral scales spiraled, colorless, whitish, or pale brown, streaked or mottled red-brown or purple, midribs green and red-brown or green and purple, ovate to elliptic, 0.8–1.5 × 0.4–0.8 mm, membranous, midrib obscure to prominent.
3–6 × 1–1.5 mm;
proximal scale 1/2 or less of spikelet length;
floral scales 6–25 per spikelet, mostly bright orange-brown, sometimes stramineous, 1.7–2.5 mm, apex subacute.
perianth bristles present or sometimes apparently absent;
stamens 3;
anthers 0.15–0.35;
styles 3-fid.
perianth bristles mostly absent or rudimentary, occasionally to 5, 1/2 of achene length, very unequal;
anthers 0.6–0.9 mm.
whitish to olive or pale brown, sometimes spotted olive or red-brown, obovoid, trigonous (or subterete), angles prominent, 0.55–0.8 × 0.3–0.5 mm, apex constricted proximal to tubercle, smooth.
medium to dark brown, obovoid to obpyriform, thickly trigonous, rarely some biconvex, angles distinct to prominent, faces convex or some plane, 0.75–1.1 × 0.55–0.7 mm, apex narrowly truncate or tapered into tubercle, rugulose at 10X to finely rough at 30X.
green or pale brown to red-brown, trigonous.
0.05–0.2 × 0.15 mm.
terminating rhizomes, 2.5–4 × 0.7–1.5 mm, body (apart from apical bud) broadly oblong to orbicular, not markedly curved.
Eleocharis microcarpa
Eleocharis coloradoensis
Varieties 2 (2 in the flora).
Specimens of Eleocharis brittonii and E. microcarpa without achenes are often difficult to distinguish. More detailed study of the four apparent entities across the two species is warranted.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Most authors, except C. L. Gilly (1941), H. L. Mason (1957), and R. R. Yeo (1980), have included Eleocharis coloradoensis in E. parvula or E. parvula var. anachaeta. In typical E. coloradoensis, which occurs from Saskatchewan south to Kansas and in California to 2100 m elevation, the achenes are usually distinctly rugulose or rough, often pitted-cellular, their apices usually truncate, and the tubercles are usually brown, often rudimentary, clearly distinct from the achene, and apparently partly sunken into the achene summit. Some plants from the southern Great Plains to the Mexican border, including the type of E. parvula var. anachaeta from Louisiana, may deserve taxonomic recognition. They differ from typical E. coloradoensis in having nearly smooth achenes with the apex tapered to a tubercle that is difficult to distinguish from the achene. C. L. Gilly (1941) separated these plants as E. membranacea (Buckley) Gilly; application of that name is doubtful because achenes are lacking from the type. R. R. Yeo (1980) studied the life-history of E. coloradoensis in the Sacramento Valley, California, and showed that it can be used to control several aquatic weeds in irrigation canals. The n = 4 count reported from Kansas under E. parvula var. anachaeta (Anonymous 1964) and on voucher specimens at GH and UC, is probably erroneous; the label on a duplicate voucher specimen at NDA includes the information “n = 3 II’s + a chain of IV” (i.e., n = 5). The record from Washington is somewhat doubtful because the specimen lacks achenes. Literature reports of E. parvula from Illinois and Tennessee may refer to E. coloradoensis; I have not seen specimens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Perianth bristles 0.2–0.4 mm, shorter than achene; proximal scale of spikelets 0.4–0.5 mm wide. | var. microcarpa |
1. Perianth bristles 0.6–1 mm, shorter than to equaling achene; proximal scale of spikelets 0.8–1 mm wide. | var. filiculmis |
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