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Engelmann's spikerush

Bolander's spikerush

Habit Plants annual, tufted. Plants perennial, densely cespitose; rhizomes caudex-like, mostly hidden by culms and roots, short, 1.5–3 mm thick, internodes very short.
Culms

terete, 2–40 cm × 0.5–1.5(2) mm.

subterete, 10–30 cm × 0.3–0.5 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.

ovoid, 3–8 × 2–3 mm;

proximal scale clasping; entire, subproximal scale with flower; floral scales 8–30, 4–5 per mm of rachilla, 2–3 × 1.5 mm;

apex entire; acute, often keeled in distal part of spike.

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.

perianth bristles 3–6, often unequal; from rudimentary to 50% of achene length;

anthers 0.9–1.4 mm;

stigmas 3.

Achenes

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

slightly to greatly compressed-trigonous, rarely thickly lenticular, 0.9–1.2 × 0.65–0.8 mm.

Distal leaf sheaths

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

persistent, not splitting;

apex obtuse, rarely hardened, lacking a tooth.

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.

flat to shallowly pyramidal; lower than wide, 0.1–0.3 × 0.4–0.65 mm.

Eleocharis engelmannii

Eleocharis bolanderi

Distribution
[WildflowerSearch map]
[BONAP county map]
[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.

Shallow, rocky, ephemeral streams. 1100–2100 m. BR, BW, Owy. CA, NV, ID; east to CO. Native.

Eleocharis bolanderi is easily recognized in summer when it forms masses of dry, brown, dormant and apparently dead culms in dry stream beds. It is easily pulled up to expose its cespitose habit. The virtually flat tubercles are particularly distinctive.

Source Flora of Oregon, volume 1, page 241
Barbara Wilson, Richard Brainerd, Nick Otting
Flora of Oregon, volume 1, page 240
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
E. acicularis, E. bella, 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
Synonyms Eleocharis engelmannii var. engelmannii, Eleocharis engelmannii var. monticola, Eleocharis obtusa var. engelmannii
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