Cyperus strigosus (Straw-colored Flatsedge)
|Also known as:||Straw-colored Umbrella Sedge|
|Habitat:||part shade, sun; wet sandy or muddy soil; shores, banks, marshes, mudflats, ditches, wet meadoes, thickets|
|Fruiting season:||August - October|
|Plant height:||4 to 40 inches|
|Wetland Indicator Status:||GP: FACW MW: FACW NCNE: FACW|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Several to numerous clusters ½ to 2 inches long at the tip of the stem, each cluster oval to cylindric with 12 to 50 spikelets (flower clusters), the spikelets arranged bottle-brush fashion on all sides of the cluster stalk, widely spreading with those at the tip erect to ascending. The 1 to 8 auxiliary clusters have stalks ¼ to 3 inches long, with 1 to 3+ clusters at the tip of a stalk, but sometimes the clusters are all congested at the tip of the stem. At the base of the group of clusters are 3 to 10 leaf-like bracts of varying lengths, M-shaped in cross-section, 2 to 10 inches long, all spreading to ascending.
Spikelets are flattened, linear-oblong in outline, 3 to 25mm (1/8 to 1 inch) long, with 3 to 11 florets, sometimes more, each subtended by a scale. Florets have 3 stamens and a 3-parted style. Scales are 3.2 to 6mm long, initially green turning straw-colored to light reddish-brown, generally oblong, with 3 or 4 ribs on each side and a green midrib that is pointed at the tip. The scales are arranged on opposite sides of the central spikelet stalk (rachilla), appressed and strongly overlapping. A narrow, papery wing runs along each side of the rachilla internode from the lower edge of the floral scale to the next scale below.
Leaves and stems:
Leaves are basal and alternate with 3 to 5 stem leaves near the base, flat, 1 to 12mm wide, 8 to 16 inches long, the longest leaves usually longer than the stem. Basal sheaths are purplish. Stems are single or multiple from the base, erect to ascending, fairly stout, 3-sided, and smooth except sometimes on the upper stem. The base of the stem is hard, swollen and bulb-like. Plants may form loose clumps and colonies from spreading rhizomes.
When mature, the floral scales drop off individually leaving the rachilla wings persisting like tiny scales on the stalk, and the lateral spikelets eventually break off at the base. Achenes are 1.8 to 2.4mm long, brown to purplish when mature, 3-sided, narrowly oblong in outline, slightly tapered to the base with a short stalk-like appendage (stipe), and more rounded at the tip.
While the swollen base of the stem is a distinctive characteristic of Cyperus strigosus, the bottle-brush like clusters are similar to other Cyperus species, notably Cyperus odoratus, Cyperus engelmannii, Cyperus esculentus and Cyperus erythrorhizos, all of which have smaller floral scales (mostly less than 3mm long). In addition, C. odoratus and C. engelmannii have spikelets that do not break off as a unit, but break apart between the florets. C. esculentus is leafier than C. strigosus and produces tubers on its roots. C. erythrorhizos has much smaller scales, 1 to 1.5mm long, that are typically more densely packed in slender cylindrical clusters and are darker reddish-brown.
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- Cyperus strigosus plant
- Cyperus strigosus plant
- Cyperus strigosus in shallow water
- Cyperus strigosus on a lake shore
- close-up of spikelet cluster
Photos by K. Chayka taken in Anoka and Ramsey counties. Photos courtesy Peter M. Dziuk taken in Chisago County. Photos by Daniel L. Nickrent and Pieter B. Pelser used by permission via PhytoImages.
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