OregonFlora: Eleocharis acicularis vs. Eleocharis ovata

	Eleocharis acicularis	Eleocharis ovata
	needle spikerush	ovoid spikerush
Habit	Plants perennial; rhizomes 0.25–0.5 mm thick, internodes 5–15 mm, sometimes with resting buds.	Plants annual, tufted.
Culms	sometimes arching; terete to sometimes distinctly compressed, 1–60 cm × 0.2–0.5(0.7) mm.	terete, 2–35 cm × 0.3–1 mm.
Spikes	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.	ovoid, 2–8 × 2–4 mm; floral scales 25–100+, approximately 10 per mm of rachilla, 1.5–2 × 1 mm; midribs often keeled in distal part of spike; apex rounded to subacute.
Flowers	perianth bristles mostly absent, uncommonly 2–4; shorter than to equaling achene; anthers 0.7–1.5 mm; stigmas 3.	perianth bristles present, rarely absent; (5)6–7, exceeding tubercle; stamens 2(3); anthers 0.3 mm; stigmas 2 or some 3.
Achenes	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.	biconvex or to 33% greatly compressed trigonous, 0.75–1 × 0.6–0.85 mm.
Distal leaf sheaths	often splitting; apex rounded (to acute).	persistent, apex of distal leaf sheath obtuse to acute; tooth to 0.2 mm.
Tubercles	pyramidal to much depressed; (0.05)0.1–0.2 × 0.15– 0.25 mm.	deltoid, 0.3–0.5 × 0.3–0.5 mm, 60% to as high as wide, 33–67% as high and 50–75% as wide as achene.
2n	=20.	=10.

	Eleocharis acicularis	Eleocharis ovata
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch map]
Discussion	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.	Freshwater shores exposed by seasonal low water levels, marshes, and disturbed wetlands. 100–1300 m. ECas, Sisk, WV. WA; north to British Columbia; northeastern North America. Native? Pacific Northwest occurrences of E. ovata are disjunct from the species northeastern North American range. This may suggest that the species is introduced in Oregon. More research is needed.
Source	Flora of Oregon, volume 1, page 240 Barbara Wilson, Richard Brainerd, Nick Otting	Flora of Oregon, volume 1, page 242 Barbara Wilson, Richard Brainerd, Nick Otting
Sibling taxa	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. 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: 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 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 ovata

needle spikerush

ovoid spikerush

Habit

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

Plants annual, tufted.

Culms

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

terete, 2–35 cm × 0.3–1 mm.

Spikes

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.

ovoid, 2–8 × 2–4 mm; floral scales 25–100+, approximately 10 per mm of rachilla, 1.5–2 × 1 mm; midribs often keeled in distal part of spike;

apex rounded to subacute.

Flowers

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

anthers 0.7–1.5 mm;

stigmas 3.

perianth bristles present, rarely absent; (5)6–7, exceeding tubercle;

stamens 2(3);

anthers 0.3 mm;

stigmas 2 or some 3.

Achenes

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.

biconvex or to 33% greatly compressed trigonous, 0.75–1 × 0.6–0.85 mm.

Distal leaf sheaths

often splitting;

apex rounded (to acute).

persistent, apex of distal leaf sheath obtuse to acute; tooth to 0.2 mm.

Tubercles

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

deltoid, 0.3–0.5 × 0.3–0.5 mm, 60% to as high as wide, 33–67% as high and 50–75% as wide as achene.

=20.

=10.

Eleocharis acicularis

Eleocharis ovata

Distribution

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

Discussion

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.

Freshwater shores exposed by seasonal low water levels, marshes, and disturbed wetlands. 100–1300 m. ECas, Sisk, WV. WA; north to British Columbia; northeastern North America. Native?

Pacific Northwest occurrences of E. ovata are disjunct from the species northeastern North American range. This may suggest that the species is introduced in Oregon. More research is needed.

Source

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

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

Sibling taxa