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Baldwin's spike-rush

pale spike-rush, wrinkle-sheath spike-rush, yellow spikerush, yellow spikesedge

Habit Plants annual(?), often mat-forming, often stoloniferous, sometimes entirely vegetative; rhizomes absent. Plants with creeping rhizomes 0.5–1 mm thick.
Culms

often arching, sometimes spotted or streaked red-brown, quadrangular or broadly elliptic, sulcate or not, 0.5–25(–30) cm × 0.1–0.4 mm, soft.

3–42 cm × 0.3–0.6 mm.

Leaves

distal leaf sheaths persistent or disintegrating, stramineous, green, red-brown, or spotted or streaked red-brown, membranous, translucent, apex obtuse or acute.

distal leaf sheaths often disintegrating, thinly membranous-translucent, inflated distally, often wrinkled, apex blunt.

Spikelets

basal spikelets usually present, pistillate; often proliferous, ovoid, ellipsoid, or linear, clearly laterally compressed, 2.3–6.9 × 0.5–2 mm, apex acute, proximal scale empty, amplexicaulous, similar to floral scales (midribs sometimes more prominent and sometimes slightly prolonged beyond lamina);

subproximal scale with a flower;

floral scales clearly distichous, 3–9, 3–4 per mm of rachilla, yellowish, pale brown, or red-brown, spotted, streaked, or mottled red-brown, narrowly ovate to oblong, (1.5–)2–5 × 0.4–0.6(–1.2) mm, membranous, apex rounded, obtuse or rarely acute, midribs keeled.

ellipsoid, 1.5–9 × 1–3.5 mm, apex acute to acuminate;

proximal scale without flower, not amplexicaulous;

floral scales to 65, 5–7 per mm of rachilla, loosely appressed to appressed, elliptic, 1–3 × 0.4–1.6 mm, membranous, apex acute.

Flowers

perianth bristles 3–7, incurved, colorless, white, or red-brown, shorter than or equaling achene;

spinules sparse, retrorse, sharply acute;

stamens 3;

anthers 1.4–2.2 mm;

styles 3-fid.

perianth bristles (0–)5–8, typically 7, white to stramineous, spinules dense to few;

styles 2-fid, rarely 3-fid.

Achenes

whitish or greenish, spotted dark green, obovoid, trigonous, angles prominent, 0.6–0.9 × 0.4–0.6 mm, apex constricted proximal to tubercle, smooth to finely cancellate at 10–20X.

stramineous to green or dark brown, biconvex, rarely trigonous, obovoid to obpryiform, 0.4–1.1 × 0.3–0.8 mm, very finely reticulate at 40X.

Tubercles

pale to red-brown, pyramidal, trigonous, 0.2–0.3(–0.4) × 0.2–0.5 mm.

whitish to stramineous or green, 0.2–0.7 × 0.2–0.4 mm, apex acute to acuminate.

Eleocharis baldwinii

Eleocharis flavescens

Phenology Fruiting early spring–winter.
Habitat Freshwater to moist terrestrial sites, pine savannas, cypress ponds, lakeshores
Elevation 0–60 m (0–200 ft)
Distribution
from FNA
AL; AR; FL; GA; LA; MS; NC; SC; TX
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; AZ; CA; CT; DE; FL; GA; ID; IL; IN; LA; MA; MD; ME; MI; MN; MS; MT; NC; NH; NJ; NY; OH; PA; RI; SC; TX; UT; VA; VT; WI; WY; NB; NS; ON; QC; South America; temperate North America; West Indies
[WildflowerSearch map]
[BONAP county map]
Discussion

Coarse plants of Eleocharis baldwinii usually bear more achenes per spikelet, dark colored achenes, culms gray-green when dried, and yellowish sheaths. Finer plants often bear few achenes per spikelet, whitish achenes, culms that are mid green when dried, and reddish sheaths. Achene color may relate to maturity, with darker achenes being fully mature. Although these variants appear to intergrade, they may be recognizable taxonomically. The longer floral scales in the spikelet are usually 3.5– 5 mm.

We have not seen vouchers to verify the report of Eleocharis baldwinii from Virginia.

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

Varieties 2 (2 in the flora).

The varieties of Eleocharis flavescens are difficult to delimit, especially in the south, and identifications of some specimens to variety are problematic.

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

Key
1. Achenes red-brown to dark brown when ripe, 0.4–0.8(–1.1) × 0.3–0.6 mm, apex rarely highly constricted proximal to tubercle; flowers with perianth bristles typically shorter than to as long as achene.
var. flavescens
1. Achenes green to golden-brown, 0.5–1.1 × 0.4–0.8 mm, often highly constricted proximal to tubercle; flowers with perianth bristles typically longer than achene.
var. olivacea
Source FNA vol. 23, p. 98. FNA vol. 23, p. 100.
Parent taxa Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Tenuissimae Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleogenus > ser. Maculosae
Sibling taxa
E. acicularis, E. aestuum, E. albida, E. ambigens, E. atropurpurea, 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. 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. 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
Subordinate taxa
E. flavescens var. flavescens, E. flavescens var. olivacea
Synonyms Chaetocyperus baldwinii Scirpus flavescens
Name authority (Torrey) Chapman: Fl. South. U.S., 519. (1860) (Poiret) Urban: Symb. Antill. 4: 116. (1903)
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