Flora of North America species comparison

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Eleocharis rostellata

Eleocharis fallax

beak spike-rush, beak spikesedge, walking sedge, walking spikerush

creeping spikerush, creeping spikesedge
Habit Plants densely tufted, mat-forming by means of rooting culm tips. Plants perennial, mat-forming; rhizomes evident, long, 1–2 mm thick, firm, cortex persistent, longer internodes 5–10(–20) mm, scales sometimes fugaceous, 5–7 mm, papery (to membranous), sometimes fibrous.
Culms

1.5–3 times as wide as thick, 20–100 cm × 0.35–2 mm, firm to hard, wiry, with to 8 subacute ribs, rarely nearly smooth;

some culms arching or decumbent and rooting at tips.

terete, often with to 12 blunt ridges when dry, 30–75 cm × 0.5–1.5 mm, firm, internally spongy.
Leaves

distal leaf sheaths not splitting abaxially, proximally dark red to brown, apex usually reddish.

distal leaf sheaths persistent, not splitting, proximally dark red, distally stramineous or green, papery to membranous, apex dark redbrown, obtuse, not callose, tooth rarely present on some culms, 0.2 mm.
Spikelets

ovoid, 5–17 × 2.5–5 mm, apex acute;

spikelets on stolons rudimentary, non-flowering, proliferous when rooting;

proximal scale empty, amplexicaulous, ovate, 2–4 mm;

subproximal scale with flower;

floral scales 20–40, 2–3 per mm of rachilla, stramineous to medium brown, midrib region paler, ovate, 3.5–6 × 2–3 mm, membranous to cartilaginous, apex entire, rounded to subacute.

ovoid or subspheric, 5–12 × 2–3(–4) mm, apex acute to obtuse;

proximal scale amplexicaulous, entire;

subproximal scale with flower;

floral scales deciduous, often spreading in fruit, 10–35, 3 per mm of rachilla, red-brown to blackish brown, midrib regions sometimes green, ovate, 2.5–3 × 1.7 mm, apex entire, obtuse to acute, often carinate in distal part of spikelet.
Flowers

perianth bristles brown, equaling achene or tubercle, densely spinulose;

anthers brown, 2–2.4 mm.

perianth bristles 1–5, brown, stout, very unequal, rudimentary to equaling achene;

stamens unknown [absent from specimens];

styles 3-fid or some 2-fid.
Achenes

often very variable within one plant, ovoid to obovoid or obpyriform, 1.5–2.5 × 1–1.2 mm, beak to 1 × 0.6 mm.

not persistent, dark yellow or medium brown, obovoid to obpyriform, compressed trigonous, or some thickly biconvex, angles evident, 1.1–1.5 × 0.95–1.25 mm, apex rounded, neck very short (to absent), finely rugulose at 10–20X, 20 or more horizontal ridges in vertical series, finely cancellate at 20–30X.
Tubercles

when present pale to dark brown, pyramidal, to 0.5 × 0.3 mm.

whitish to brown, pyramidal, not depressed, as high as wide, 0.3–0.5 × 0.4–0.6 mm.
2n

= 42.

Eleocharis rostellata

Eleocharis fallax
Phenology Fruiting late spring in south, summer–fall in north. Fruiting late summer.
Habitat Very wet calcareous or brackish fens, springs, shores Coastal, fresh to brackish pond and lakeshores, marsh
Elevation 50–2400 m (200–7900 ft) 0–10 m (0–0 ft)
Distribution
from FNA
AZ; CA; CT; DE; FL; ID; IL; IN; KS; LA; MA; MD; ME; MI; MN; MT; NC; NE; NJ; NM; NV; NY; OH; OK; PA; RI; SC; SD; TX; UT; VA; WA; WI; WY; BC; NS; ON; Mexico; West Indies (Cuba, Haiti, Puerto Rico)
[WildflowerSearch map]
[BONAP county map]
from FNA
MA; NJ; NS
[BONAP county map]
Discussion

Eleocharis rostellata is highly competitive, often forming large monospecific colonies. The South American E. platypus C. B. Clarke is often treated as a synonym of E. rostellata. Eleocharis rostellata superfically closely resembles E. suksdorfiana in its culms, spikelets, and achenes, but differs in the absence of creeping rhizomes, presence of stoloniferous culms, absence of a flower in the proximal scale, and achene surface details. The collection of E. rostellata I have seen from Miami-Dade County, Florida, is from 1877. I have not seen vouchers for Archuleta County, Colorado, by H. D. Harrington (1954), or for the localities in Montana and South Carolina, which are based on the map in H. K. Svenson (1934).

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

Of conservation concern.

The taxonomic status of Eleocharis fallax is problematic. I have seen only the type, from 1919 from a pond on Cape Cod, Massachusetts; a specimen from 1955 from Inverness County, Nova Scotia; and a specimen from the Passaic River marshes in New Jersey. It is reportedly extirpated from the type locality (M. L. Fernald 1950). Another specimen from Cape Cod is typical of E. fallax except for some lenticular achenes. I have not seen a voucher for the material, reportedly collected by H. K. Svenson from a brackish marsh on Plum Island, Essex County, Massachusetts, from which S.-O. Strandhede (1967) counted the chromosome number. It seems possible that these collections are of hybrid origin from E. elliptica and either E. erythropoda or E. uniglumis var. halophila (M. L. Fernald 1950). The plants are similar to E. erythropoda except for their trigonous, rougher achenes and sometimes fibrous rhizome scales, which suggests introgression from E. elliptica. Because some specimens of E. ambigens, including the type, have mixtures of lenticular and trigonous achenes, E. fallax is often treated as conspecific with E. ambigens, from which it differs only in its 3-fid styles, trigonous, more rugulose achenes, and higher tubercles. It seems best to recognize E. fallax as a species pending further research because the plants bear many, apparently normal achenes and are not exactly intermediate between their putative parents, and to avoid using a name for the widespread E. ambigens that may apply only to rare hybrids.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 23, p. 90. FNA vol. 23, p. 78.
Parent taxa Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Rostellatae Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. 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. parvula, E. quadrangulata, E. quinqueflora, E. radicans, E. ravenelii, E. retroflexa, E. reverchonii, E. robbinsii, 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. diandra, E. elliptica, E. elongata, E. engelmannii, E. equisetoides, E. erythropoda, 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 rostellatus
Name authority (Torrey) Torrey: Fl. New York 2: 347. (1843) Weatherby: Rhodora 24: 23. (1922)
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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