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knotted spikerush

few-flower spike-rush, few-flower spikesedge, éléocharide à cinq fleurs

Habit Plants perennial; rhizomes 2–4 mm thick, firm, longer internodes 3–7.5 cm, scales 5 mm, tubers absent. Plants perennial; rhizomes 0.2–1 mm thick, scales persistent or fugaceous, 2–4(–7) mm, thinly membranous, not fibrous; resting buds often present on rhizomes or among culm bases, broadly to narrowly ovoid, 3–6(–10) × 2–5 mm; caudices absent, rarely present, soft or rarely hard, 0.5 mm thick.
Culms

terete, 45–100 cm × (3.2–)5–9.4 mm, soft to firm, sometimes septate-nodulose proximally, not distally, internally hollow with complete transverse septa, closer together near the spikelet, evident externally;

plants never forming filiform, flaccid culms.

erect, not spirally twisted, not contracted near spikelet, when dry usually with several blunt to acute ridges and sulcate, subterete to slightly compressed, to 2 times wider than thick, 5–35 cm × 0.2–0.5(–1.2) mm, soft to hard;

culm tufts often proximally bulbous (if bulbous then tunicated by papery-fibrous scales).

Leaves

distal leaf sheaths persistent, membranous to thinly papery, apex acute to acuminate.

distal leaf sheaths stramineous to brown or reddish proximally, green to stramineous or brown distally, membranous to papery, apex often reddish, subtruncate to acute.

Spikelets

not proliferous, (20–)40–62 × 4–7 mm;

rachilla joints bearing prominent wing-like remnants of floral scales;

proximal scale empty, amplexicaulous, (3–)3.5–5 mm;

floral scales 115–220, 1–3 per mm of rachilla, stramineous to pale brown, usually with pale to dark brown submarginal band, midrib region sometimes greenish, obovate to broadly oblong, (4–)4.5–5 × 2.8–4 mm, cartilaginous, often membranous toward margins, margins broadly translucent, membranous, apex rounded to subacute.

3–8 × 1.5–4 mm;

proximal scale with a flower, seldom empty, 2–5 mm, 1/2 or more as long as spikelet;

floral scales 3–10 per spikelet, 2.5–6 × 1.5–2.5 mm.

Flowers

perianth bristles 6–8, stramineous, stout, flattened, subequal, exceeding achene, to 2.9 mm, coarsely spinulose;

anthers stramineous to reddish, 2.5–5 mm;

styles 2-fid or 3-fid.

perianth bristles (0–)3–6, often unequal, rudimentary to equaling tubercle, stout to slender, spinules dense to apparently absent;

anthers 1.5–2.7(–3.5) mm.

Achenes

stramineous to golden-yellow or reddish brown or gray, obovoid to obpyriform, biconvex or nearly plano-convex, often with abaxial longitudinal ridge, 1.4–1.8(–2) × 1.1–1.4 mm, markedly sculptured at 10–15X, each face with 23–37 rows of transversely elongated cells, the longitudinal walls separating the cells often prominent, apex with short neck 0.7–0.8 mm wide.

stramineous to medium brown or gray-brown, equilaterally trigonous to compressed-trigonous, rarely some biconvex, obpyriform (to obovoid), 1.6–2.3 × 0.7–1.3 mm, beak variable.

Tubercles

dark brown, lamelliform, slightly higher than wide, 0.7–1.1 × 0.5–0.7 mm.

rarely absent, 0.3–0.4 × 0.2–0.3 mm.

Eleocharis interstincta

Eleocharis quinqueflora

Phenology Fruiting late spring–winter. Fruiting (spring–)summer.
Habitat Fresh ponds, lakeshores, marshes, springs, ditches, canals Fens, wet meadows, seeps, springs, hot springs
Elevation 10–500 m (0–1600 ft) 0–3600 m (0–11800 ft)
Distribution
from FNA
FL; OK; TX; Mexico; Central America; e South America
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from FNA
AK; AZ; CA; CO; IA; ID; IL; IN; MA; ME; MI; MN; MT; NE; NH; NJ; NM; NV; NY; OH; OR; PA; UT; VT; WA; WI; WY; AB; BC; MB; NB; NL; NS; NT; ON; PE; QC; SK; YT; Greenland; Eurasia
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Discussion

Contrary to statements in the literature, sectioning reveals that the culm septa are closer together near the spikelet than in the rest of the culm in both Eleocharis interstincta and E. equisetoides.

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

The chromosome numbers for Eleocharis quinqueflora reported for North America (2n = 80) are in doubt because vouchers and other information are lacking. The often-cited n = 10 is probably erroneous. S.-O. Strandhede and R. M. T. Dahlgren (1968) gave 2n = 132 and 134 from Scandinavia. Recognition of infraspecific taxa within E. quinqueflora is premature pending a worldwide revision of subg. Zinserlingia. It has been reported from North Dakota, although I have not seen specimens. About five varieties and subspecies of E. quinqueflora have been described worldwide.

Most specimens from eastern North America and some from the West can be placed in Eleocharis quinqueflora subsp. fernaldii (Svenson) Hultén, which is characterized by its small size (culms to 15 cm × 0.5 mm) and small bulbs. Specimens of E. quinqueflora from 2000–3600 m in California, which are atypical, especially in that the proximal scales of the spikelets do not subtend flowers, may deserve taxonomic recognition. Those plants are also small, with culms only to 15 cm × 0.5 mm; hard caudices are often present at the culm-tuft bases; small, narrowly ovoid bulbs are sometimes present; and perianth bristles are absent or rudimentary. Very few specimens of E. quinqueflora are intermediate with E. suksdorfiana.

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

Source FNA vol. 23, p. 119. FNA vol. 23, p. 114.
Parent taxa Cyperaceae > Eleocharis > subg. Limnochloa Cyperaceae > Eleocharis > subg. Zinserlingia
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. 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. 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. 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 interstinctus Scirpus quinqueflorus, E. fernaldii, E. pauciflora, E. pauciflora var. fernaldii, E. quinqueflora subsp. fernaldii
Name authority (Vahl) Roemer & Schultes: in J. J. Roemer et al., Syst. Veg. 2: 149. (1817) (Hartmann) O. Schwarz: Mitt. Thüring. Bot. Ges. 1: 89. (1949)
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