OregonFlora: Eleocharis engelmannii

	Eleocharis engelmannii
	Engelmann's spikerush
Habit	Plants annual, tufted.
Culms	terete, 2–40 cm × 0.5–1.5(2) mm.
Spikes	lanceoloid to subcylindric, 5–10(20) × 2–3(4) mm; proximal scale empty, encircling approximately 67% of culm; floral scales 25–100(200), 8–12 per mm of rachilla, 2(2.5) × 1–1.3 mm; apex narrowly rounded to subacute.
Flowers	perianth bristles present or often absent; (0)5–8; about as long as the achenes; anthers 0.3–0.7(1) mm; stigmas 2–3.
Achenes	biconvex or to 33% greatly compressed trigonous, 0.9–1.1(1.5) × 0.7– 1.1 mm.
Distal leaf sheaths	persistent, apex of distal leaf sheath obtuse to acute, with tooth to 0.3 mm.
Tubercles	depressed, subdeltoid, 0.1–0.3(0.4) × 0.6–0.9(1) mm, 10–40% as high as wide, 25% or less as high as achene, 90% as wide as achene.

	Eleocharis engelmannii
Distribution	[WildflowerSearch map] [BONAP county map]
Discussion	Freshwater shores exposed by seasonal low water levels, marshes, disturbed wetlands. 50–500 m. WV. CA, ID, WA; north to British Columbia, east to MA, southeast to AL. Native. Eleocharis engelmannii is similar to E. ovata and the much more common E. obtusa but has markedly shorter tubercles and usually more cylindric spikes.
Source	Flora of Oregon, volume 1, page 241 Barbara Wilson, Richard Brainerd, Nick Otting
Sibling taxa	E. acicularis, E. bella, E. bolanderi, E. decumbens, E. erythropoda, E. macrostachya, E. obtusa, E. ovata, E. palustris, E. parishii, E. parvula, E. quadrangulata, E. quinqueflora, E. rostellata, E. suksdorfiana
Synonyms	Eleocharis engelmannii var. engelmannii, Eleocharis engelmannii var. monticola, Eleocharis obtusa var. engelmannii
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

Eleocharis engelmannii

Engelmann's spikerush

Habit

Plants annual, tufted.

Culms

terete, 2–40 cm × 0.5–1.5(2) mm.

Spikes

lanceoloid to subcylindric, 5–10(20) × 2–3(4) mm;

proximal scale empty, encircling approximately 67% of culm; floral scales 25–100(200), 8–12 per mm of rachilla, 2(2.5) × 1–1.3 mm;

apex narrowly rounded to subacute.

Flowers

perianth bristles present or often absent; (0)5–8; about as long as the achenes;

anthers 0.3–0.7(1) mm;

stigmas 2–3.

Achenes

biconvex or to 33% greatly compressed trigonous, 0.9–1.1(1.5) × 0.7– 1.1 mm.

Distal leaf sheaths

persistent, apex of distal leaf sheath obtuse to acute, with tooth to 0.3 mm.

Tubercles

depressed, subdeltoid, 0.1–0.3(0.4) × 0.6–0.9(1) mm, 10–40% as high as wide, 25% or less as high as achene, 90% as wide as achene.

Eleocharis engelmannii

Distribution

[WildflowerSearch map]

[BONAP county map]

Discussion

Freshwater shores exposed by seasonal low water levels, marshes, disturbed wetlands. 50–500 m. WV. CA, ID, WA; north to British Columbia, east to MA, southeast to AL. Native.

Eleocharis engelmannii is similar to E. ovata and the much more common E. obtusa but has markedly shorter tubercles and usually more cylindric spikes.

Source

Flora of Oregon, volume 1, page 241
Barbara Wilson, Richard Brainerd, Nick Otting

Sibling taxa