Species: Eleocharis compressa Sullivan

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Eleocharis compressa Sullivan

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TAXONOMY

Family:

Cyperaceae

Genus:

Eleocharis

Species Synonyms:

Eleocharis tenuis var. atrata (Svens.) Boivin
Eleocharis acuminata (Muhl.) Nees
Eleocharis compressa var. atrata Svens.
Eleocharis elliptica var. compressa (Sullivan) Drapalik & Mohlenbroc

Common Names:

flatstem spikerush
flatstemmed spikesedge
flattened spike-rush

DISTRIBUTION

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

HABITAT

Saskatchewan:

wet boggy or springy, usually calcareous or alkaline areas

Associated Species:

Baltic rush, Canadian horseweed, common spikerush, dandelion, hawksbeard, Dudley’s rush, fowl bluegrass, prickly rose, silverberry, scratchgrass, small leaf everlasting, smooth brome, Torrey’s sedge, western snowberry

RARITY STATUS

Provincial Status According
to Harms (2003):

Endangered

Nature Conservancy Status:

Saskatchewan Species at
Risk Status:

None

COSEWIC Status:

None

Flatstem spikerush is endangered in Saskatchewan because it is rare or uncommon and most local populations are small. No immediate threats are known for this species.

SPECIES DESCRIPTION

Height:

8 - 60 cm

Roots:

rhizome stout, firm, cortex persistent, scales decaying to fibres

Stems:

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 spikelet axis, spirally arranged, spreading in fruit, medium to dark brown, occasionally straw-coloured or colourless, apex tapered to a long or short point and hyaline and often toothed or jagged

Flowers:

perfect; perianth bristles 0 – 5, early deciduous, straw-coloured, shorter than to equaling achene, bearing small spines; stamens 3, anthers yellow to orange-brown; styles 3-fid

Achenes:

1 – 1.3 mm long, inversely egg-shaped, bluntly three-sided, yellowish-brown or dark brown; swelling at base of style short, brown to whitish

ELEOCHARIS KEY FOR SPECIES FOUND IN SASKATCHEWAN

1 Achenes with 9 – 13 longitudinal rows of horizontal ridges between prominent longitudinal ridges and achene angles; spikelets with lowest scale always subtending a flower; stems to 1.5 mm wide	E. acicularis
1 Achenes without long rows of horizontal ridges; lowest scale subtending a flower or empty; stems to 5 mm wide	2

2 Swelling at tip of achene conical, confluent with achene; stigmas 3	3
2 Swelling at tip of achene well-differentiated; stigmas 2 or 3	4

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 convex	5
4 Styles 3-fid; achenes three-sided	7

5 Tufted annuals, roots fibrous; achenes green, straw-coloured, or black; anthers 0.2 – 1 mm long	E. engelmannii
5 Perennials with rhizomes or runners; achenes yellow to dark brown; anthers 1 – 2.5 mm long	6

6 Tip of uppermost leaf sheath with distinct tooth on all or some stems; base of spikelet with single empty scale nearly enclosing stem	E. erythropoda
6 Tip of distal leaf sheath without distinct tooth on all stems; 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

8 Achene surface honey-comb netted; swelling at tip of achene broader than high; stems to 90 cm tall	E. elliptica
8 Achene surface minutely wrinkled or roughened but not netted; swelling at tip of achene longer than broad; stems to 40 cm tall	9

9 Spikelets < 5 mm long; stems 4-angled and capillary	E. nitida
9 Spikelets to greater than 1 cm long; stems flat and wiry	E. compressa