OregonFlora: Eleocharis pachycarpa vs. Eleocharis parvula

	Eleocharis pachycarpa	Eleocharis parvula
		small spikerush
Habit		Plants perennial, rhizomatous, internodes to 4 cm; tubers terminating rhizomes usually markedly J- or horseshoe-shaped, body (apart from apical bud) oblong, 2–2.5(5) × 0.5–1 mm; tubers among culm bases straight, narrowly fusiform, 4–5 mm.
Culms		terete, 2–9 cm × 0.2–0.5 mm.
Spikes		2–4 × 1–2 mm; proximal scale 50% or more of spike length; floral scales 6–10 per spike, 1.4–2.7 mm; apex rounded to subacute.
Flowers		perianth bristles 6, usually equaling achene to slightly exceeding tubercle, sometimes unequal and some 50% of achene; very rarely rudimentary; anthers 0.7–1.2 mm; stigmas (2)3.
Achenes		thickly trigonous, 0.9–1.2 × 0.55–0.75 mm.
Distal leaf sheaths		often disintegrating, thinly membranous; apex rounded.
Tubercles		0.1–0.2 × 0.15 mm.

	Eleocharis pachycarpa	Eleocharis parvula
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion		Brackish or saline tidal marshes and other coastal wetlands. 0–50 m. Est. CA, WA; throughout much of North America; Eurasia. Native. When growing submerged in deeper water, the plants may not produce spikes and can be confused with E. acicularis and Schoenoplectus subterminalis.
Source		Flora of Oregon, volume 1, page 242 Barbara Wilson, Richard Brainerd, Nick Otting
Sibling taxa	E. acicularis, E. bella, E. bolanderi, E. decumbens, E. engelmannii, E. erythropoda, E. macrostachya, E. obtusa, E. ovata, E. palustris, E. parishii, E. parvula, E. quadrangulata, E. quinqueflora, E. rostellata, E. suksdorfiana	E. acicularis, E. bella, E. bolanderi, E. decumbens, E. engelmannii, E. erythropoda, E. macrostachya, E. obtusa, E. ovata, E. palustris, E. parishii, E. quadrangulata, E. quinqueflora, E. rostellata, E. suksdorfiana
Synonyms		Eleocharis parvula var. parvula, Scirpus nanus
Web links	Local floras: CA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Eleocharis pachycarpa

Eleocharis parvula

small spikerush

Habit

Plants perennial, rhizomatous, internodes to 4 cm; tubers terminating rhizomes usually markedly J- or horseshoe-shaped, body (apart from apical bud) oblong, 2–2.5(5) × 0.5–1 mm; tubers among culm bases straight, narrowly fusiform, 4–5 mm.

Culms

terete, 2–9 cm × 0.2–0.5 mm.

Spikes

2–4 × 1–2 mm;

proximal scale 50% or more of spike length; floral scales 6–10 per spike, 1.4–2.7 mm;

apex rounded to subacute.

Flowers

perianth bristles 6, usually equaling achene to slightly exceeding tubercle, sometimes unequal and some 50% of achene; very rarely rudimentary;

anthers 0.7–1.2 mm;

stigmas (2)3.

Achenes

thickly trigonous, 0.9–1.2 × 0.55–0.75 mm.

Distal leaf sheaths

often disintegrating, thinly membranous;

apex rounded.

Tubercles

0.1–0.2 × 0.15 mm.

Eleocharis pachycarpa

Eleocharis parvula

Distribution

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

Brackish or saline tidal marshes and other coastal wetlands. 0–50 m. Est. CA, WA; throughout much of North America; Eurasia. Native.

When growing submerged in deeper water, the plants may not produce spikes and can be confused with E. acicularis and Schoenoplectus subterminalis.

Source

Flora of Oregon, volume 1, page 242
Barbara Wilson, Richard Brainerd, Nick Otting

Sibling taxa