OregonFlora: Eleocharis rostellata vs. Eleocharis melanocarpa

	Eleocharis rostellata	Eleocharis melanocarpa
	walking sedge, walking spikerush
Habit	Plants densely tufted, stoloniferous, mat-forming by means of rooting culm tips.
Culms	1.5–3 times as wide as thick, 20–100 cm × 0.35–2 mm; wiry; some culms arching or decumbent and rooting at tips.
Spikes	5–17 × 2.5–5 mm; spikes on stolons rudimentary and sometimes producing bulbs; proximal scale empty; amplexicaul, 2–4 mm, subproximal scale with flower; floral scales 20–40, 2–3 per mm of rachilla, 3.5–6 × 2–3 mm; apex entire, rounded to subacute.
Flowers	perianth bristles, equaling achene or tubercle; anthers 2–2.4 mm; stigmas 3.
Achenes	often very variable within one plant, 1.5–2.5 × 1–1.2 mm; beak to 1 × 0.6 mm.
Distal leaf sheaths	not splitting; apex usually reddish.
Tubercles	when present pyramidal; to 0.5 × 0.3 mm.

	Eleocharis rostellata	Eleocharis melanocarpa
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion	Wet, often alkaline soils on shorelines and around springs and fens. 50–1500 m. BR, Col, ECas, Owy. CA, ID, NV, WA; north to British Columbia, east to New Brunswick, south to Mexico and West Indies. Native. When not producing stolons, E. rostellata can resemble E. suksdorfiana, but the latter species has a flower in the proximal scale. Eleocharis rostellata can form large pure stands.
Source	Flora of Oregon, volume 1, page 243 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. suksdorfiana	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
Web links	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	Local Web sites: 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 melanocarpa

walking sedge, walking spikerush

Habit

Plants densely tufted, stoloniferous, mat-forming by means of rooting culm tips.

Culms

1.5–3 times as wide as thick, 20–100 cm × 0.35–2 mm; wiry; some culms arching or decumbent and rooting at tips.

Spikes

5–17 × 2.5–5 mm;

spikes on stolons rudimentary and sometimes producing bulbs;

proximal scale empty; amplexicaul, 2–4 mm, subproximal scale with flower; floral scales 20–40, 2–3 per mm of rachilla, 3.5–6 × 2–3 mm;

apex entire, rounded to subacute.

Flowers

perianth bristles, equaling achene or tubercle;

anthers 2–2.4 mm;

stigmas 3.

Achenes

often very variable within one plant, 1.5–2.5 × 1–1.2 mm;

beak to 1 × 0.6 mm.

Distal leaf sheaths

not splitting;

apex usually reddish.

Tubercles

when present pyramidal; to 0.5 × 0.3 mm.

Eleocharis melanocarpa

Distribution

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

Wet, often alkaline soils on shorelines and around springs and fens. 50–1500 m. BR, Col, ECas, Owy. CA, ID, NV, WA; north to British Columbia, east to New Brunswick, south to Mexico and West Indies. Native.

When not producing stolons, E. rostellata can resemble E. suksdorfiana, but the latter species has a flower in the proximal scale. Eleocharis rostellata can form large pure stands.

Source

Flora of Oregon, volume 1, page 243
Barbara Wilson, Richard Brainerd, Nick Otting

Sibling taxa