Eleocharis compressa Sullivan
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Family: Cyperaceae
Genus: Eleocharis
Species Synonyms: Eleocharis tenuis var. atrata (Svens.) Boivin
Eleocharis acuminata (Muhl.) Nees
Eleocharis compressa var. atrata Svens.
Eleocharis elliptica E var. compressa (Sullivan) Drapalik & Mohlenbrock
Common Names: flatstem spikerush
flatstemmed spikesedge
flattened spike-rush
Canada: British Columbia – southern Saskatchewan – Quebec
Saskatchewan: southern Saskatchewan; Plunkett, north of Hudson Bay Jct. – Souris River Valley
Ecoregion: Moist Mixed Grassland, Aspen Parkland, Mid-Boreal Upland
Saskatchewan: wet boggy or springy, usually calcareous or alkaline areas
Associated Species: Antennaria microphylla, Bromus inermis, Carex torreyi, Conyza canadensis . canadensis, Crepis runcinata, Elaeagnus commutata, Eleocharis palustris, Juncus balticus, Juncus dudleyi, Muhlenbergia asperifolia, Poa palustris, Rosa acicularis, Rosa woodsii, Symphoricarpos occidentalis
Provincial Status According
to Harms (2003):
Nature Conservancy Status:
Saskatchewan Species at
Risk Status:
Eleocharis compressa is endangered in Saskatchewan because it is rare or uncommon and most local populations are small. No immediate threats are known for this species.
Height: 8 - 60 cm
Roots: rhizome stout, firm, cortex persistent, scales decaying to fibres
Culms: perennial, mat-forming, compressed, wiry, to 5 times as wide as thick, firm, 2 – 12-ribbed
Leaves: blade bearing leaves absent; lower leaf sheaths persistent, reddish at top, green to reddish at bottom, papery
Inflorescence: spikelet terminal, solitary, erect
Spikelets: 4 – 12 mm, ovoid; floral scales 20 – 60, 6 per mm of rachilla, spirally arranged, spreading in fruit, medium to dark brown, occasionally stramineus or colourless, apex acute to acuminate and hyaline, often toothed or lacerate
Flowers: perfect; perianth bristles 0 – 5, early deciduous, stramineus, shorter than to equalling achene, spinulose; stamens 3, anthers yellow to orange-brown; styles 3-fid
Achenes: 1 – 1.3 mm long, obovoid, bluntly trigonous, yellowish-brown or dark brown; tubercles short, brown to whitish
1 Achenes with 9 – 13 longitudinal rows of horizontal ridges between prominent longitudinal ridges and achene angles; spikelets with proximal scale always subtending a flower; culms to 1.5 mm wide
E. acicularis
1 Achenes without long rows of horizontal ridges; proximal scale subtending a flower or empty; culms to 5 mm wide
2 Tubercle conical, confluent with achene; stigmas 3
2 Large shrub; leaflets lobed, less than 3 cm long; fruits red and hairy
3 Spikelets to 3 mm long, internodes equal in thickness and length throughout the spikelet; scales 5 – 500 per spikelet, green or pale brown; stems < 10 cm tall; rhizome lacking a bulb
E. parvula
3 Spikelets to 7 mm long, proximal internodes thicker and shorter than internodes in the middle of the spikelet; scales 4 – 12 per spikelet, tinged with purple or brown; stems to 40 cm tall; rhizomes bulbous
E. quinquefolia
4 Styles 2-fid; achenes biconvex
4 Styles 3-fid; achenes trigonous
5 Tufted annuals, roots fibrous; achenes green, stramineus, or black; anthers 0.2 – 1 mm long
E. engelmannii
5 Perennials with rhizomes or stolons; achenes yellow to dark brown; anthers 1 – 2.5 mm long
6 Apex of distal leaf sheath with distinct tooth on all or some culms; base of spikelet with single empty scale nearly enclosing culm
E. erythropoda
6 Apex of distal leaf sheath without distinct tooth on all culms; base of spikelet with 2 or 3 firm, empty scales
E. palustris
7 Achenes biconvex (or < 1/3 of achenes trigonous); tufted annuals; spikelets never proliferous
E. engelmannii
7 Achenes trigonous; annuals or perennials, rhizomatous or stoloniferous; spikelets may be proliferous
8 Achene surface honey-comb reticulate; tubercle broader than high; culms to 90 cm tall
E. elliptica
8 Achene surface minutely wrinkled or roughened but not reticulate; tubercle longer than broad; culms to 40 cm tall
9 Spikelets < 5 mm long; culms 4-angled and capillary
E. nitida
9 Spikelets to greater than 1 cm long; culms flat and wiry
E. compressa