Flora of North America species comparison

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Eleocharis geniculata

Eleocharis coloradoensis

bent spike-rush, Canada spikesedge, capitate spike-rush

dwarf spike-rush
Habit Plants tufted, without creeping rhizomes.
Culms

to 45 cm × 0.2–1 mm.

Leaves

distal leaf sheaths persistent, firm, distally tightly sheathing, apex acute.

Spikelets

orbicular to ovoid, 1–9 × 1–4 mm, apex rounded to acute;

proximal scale without flower, not amplexicaulous;

floral scales to 125, 11–14 per mm of rachilla, tightly appressed, dark red-brown to stramineous, ovate to elliptic, 0.8–3 × 0.6–2(–2.3) mm, membranous to cartilaginous, apex rounded to acute.

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.
Flowers

perianth bristles (0–)4–8, typically 7, red-brown, rarely whitish, vestigial to much exceeding tubercle, typically equaling achene, spinules few to dense;

styles 2-fid.

perianth bristles mostly absent or rudimentary, occasionally to 5, 1/2 of achene length, very unequal;

anthers 0.6–0.9 mm.
Achenes

brown ripening to black, biconvex, orbicular to obpyriform, 0.5–1.1 × 0.3–0.7 mm, apex rarely constricted proximal to tubercle, very finely reticulate at 40X.

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.
Tubercles

stramineous to whitish, umbonate to subconic, 0.2–0.4 × 0.2–0.5 mm, apex rounded to acute.

0.05–0.2 × 0.15 mm.
Tubers

terminating rhizomes, 2.5–4 × 0.7–1.5 mm, body (apart from apical bud) broadly oblong to orbicular, not markedly curved.
2n

= 10.

Eleocharis geniculata

Eleocharis coloradoensis
Phenology Fruiting spring–winter (Mar–Dec). Fruiting summer–fall (north), spring–fall (far south).
Habitat Brackish creeks, canal banks, dune depressions, hammocks, irrigation ditches, lakeshores, lagoons, mangrove thickets, maritime mud flats, ditches, salt marshes Fresh or brackish drying lake and pond margins, stream beds, flood plains, vernal pools, irrigation ditches, tidal wetlands
Elevation 0–1500 m [0–4900 ft] 0–2100 m [0–6900 ft]
Distribution
from FNA
AL; AZ; CA; FL; GA; IL; IN; LA; MI; MS; NE; NM; NV; OH; OK; PA; TX; ON; Mexico; Central America; South America; West Indies; Bermuda; Asia; Africa; Pacific Islands
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; CA; CO; IA; ID; KS; LA; MN; MO; MS; ND; NM; NV; OK; OR; SD; TX; UT; MB; SK; Mexico
Discussion

The name Eleocharis caribaea (Rottbøll) S. F. Blake is considered by most contemporary authorities to be misapplied (K. L. Wilson 1990). Eleocharis geniculata has been reported from South Carolina; I have not seen a voucher.

(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.)
Source FNA vol. 23, p. 101. FNA vol. 23, p. 106.
Parent taxa Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Maculosae Cyperaceae > Eleocharis > subg. Eleocharis > sect. Parvulae
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. 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
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. 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. 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 geniculatus, E. capitata, E. caribaea, E. dispar Scirpus coloradoensis, E. parvula var. anachaeta
Name authority (Linnaeus) Roemer & Schultes: in J. J. Roemer et al., Syst. Veg. 2: 150. (1817) (Britton) Gilly: Amer. Midl. Naturalist 26: 66. (1941)
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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