OregonFlora: Eleocharis bolanderi vs. Eleocharis acicularis

	Eleocharis bolanderi	Eleocharis acicularis
	Bolander's spikerush	needle spikerush
Habit	Plants perennial, densely cespitose; rhizomes caudex-like, mostly hidden by culms and roots, short, 1.5–3 mm thick, internodes very short.	Plants perennial; rhizomes 0.25–0.5 mm thick, internodes 5–15 mm, sometimes with resting buds.
Culms	subterete, 10–30 cm × 0.3–0.5 mm.	sometimes arching; terete to sometimes distinctly compressed, 1–60 cm × 0.2–0.5(0.7) mm.
Spikes	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.	2–8 × 1–2 mm; floral scales 4–25, 4–6 per mm of rachilla, 1.5–2.5(3.5) × 1–1.5 mm; apex blunt to acute.
Flowers	perianth bristles 3–6, often unequal; from rudimentary to 50% of achene length; anthers 0.9–1.4 mm; stigmas 3.	perianth bristles mostly absent, uncommonly 2–4; shorter than to equaling achene; anthers 0.7–1.5 mm; stigmas 3.
Achenes	slightly to greatly compressed-trigonous, rarely thickly lenticular, 0.9–1.2 × 0.65–0.8 mm.	with angles plus about 8–12 obscure to prominent longitudinal ridges, narrowly to broadly obovoid to obpyriform, 0.7–1.1 × 0.35–0.6 mm; fine horizontal ridges 30–60, clearly evident to crowded and obscure; spaces between trabeculae sometimes translucent.
Distal leaf sheaths	persistent, not splitting; apex obtuse, rarely hardened, lacking a tooth.	often splitting; apex rounded (to acute).
Tubercles	flat to shallowly pyramidal; lower than wide, 0.1–0.3 × 0.4–0.65 mm.	pyramidal to much depressed; (0.05)0.1–0.2 × 0.15– 0.25 mm.
2n		=20.

	Eleocharis bolanderi	Eleocharis acicularis
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion	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.	Ponds, shallow wetlands, and exposed shorelines and mudflats, vernal pools, and other, often disturbed wetlands. 0–2300 m. All ecoregions except Col. CA, ID, NV, WA; north to AK, east to Greenland and GA, south to South America; Australia, Eurasia. Native. Plants of this species frequently grow as submerged or floating mats that do not flower. These plants differ from typical E. acicularis in having terete, smooth, soft, translucent culms with conspicuous partitions between the air cavities. Such plants are difficult to identify and can be confused with Schoenoplectus subterminalis. Eleocharis acicularis is highly variable, but much of the variation is probably environmental, dependent particularly on water depth. As a result of this plasticity, recognition of any of the described varieties is likely unwarranted. Eleocharis bella is similar but annual, cespitose, only occasionally produces rhizomes and has smaller floral scales, anthers, and achenes.
Source	Flora of Oregon, volume 1, page 240 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. 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. 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
Synonyms		Eleocharis acicularis var. acicularis, Eleocharis acicularis var. occidentalis
Web links	Local floras: 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 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 acicularis

Bolander's spikerush

needle spikerush

Habit

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

Plants perennial; rhizomes 0.25–0.5 mm thick, internodes 5–15 mm, sometimes with resting buds.

Culms

subterete, 10–30 cm × 0.3–0.5 mm.

sometimes arching; terete to sometimes distinctly compressed, 1–60 cm × 0.2–0.5(0.7) mm.

Spikes

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.

2–8 × 1–2 mm; floral scales 4–25, 4–6 per mm of rachilla, 1.5–2.5(3.5) × 1–1.5 mm;

apex blunt to acute.

Flowers

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

anthers 0.9–1.4 mm;

stigmas 3.

perianth bristles mostly absent, uncommonly 2–4; shorter than to equaling achene;

anthers 0.7–1.5 mm;

stigmas 3.

Achenes

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

with angles plus about 8–12 obscure to prominent longitudinal ridges, narrowly to broadly obovoid to obpyriform, 0.7–1.1 × 0.35–0.6 mm; fine horizontal ridges 30–60, clearly evident to crowded and obscure; spaces between trabeculae sometimes translucent.

Distal leaf sheaths

persistent, not splitting;

apex obtuse, rarely hardened, lacking a tooth.

often splitting;

apex rounded (to acute).

Tubercles

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

pyramidal to much depressed; (0.05)0.1–0.2 × 0.15– 0.25 mm.

=20.

Eleocharis bolanderi

Eleocharis acicularis

Distribution

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

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.

Ponds, shallow wetlands, and exposed shorelines and mudflats, vernal pools, and other, often disturbed wetlands. 0–2300 m. All ecoregions except Col. CA, ID, NV, WA; north to AK, east to Greenland and GA, south to South America; Australia, Eurasia. Native.

Plants of this species frequently grow as submerged or floating mats that do not flower. These plants differ from typical E. acicularis in having terete, smooth, soft, translucent culms with conspicuous partitions between the air cavities. Such plants are difficult to identify and can be confused with Schoenoplectus subterminalis. Eleocharis acicularis is highly variable, but much of the variation is probably environmental, dependent particularly on water depth. As a result of this plasticity, recognition of any of the described varieties is likely unwarranted. Eleocharis bella is similar but annual, cespitose, only occasionally produces rhizomes and has smaller floral scales, anthers, and achenes.

Source

Flora of Oregon, volume 1, page 240
Barbara Wilson, Richard Brainerd, Nick Otting

Sibling taxa