Cyperus diandrus (Umbrella Flatsedge)

Plant Info
Also known as: Slender Flatsedge
Family:Cyperaceae (Sedge)
Life cycle:annual
Habitat:sun; wet sandy or peaty soil; muddy shores, banks, sloughs
Fruiting season:August - October
Plant height:1 to 10 inches
Wetland Indicator Status:GP: FACW MW: FACW NCNE: OBL
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: indistinct Cluster type: panicle Cluster type: spike

[photo of flowering clusters] 2 to 7 clusters up to ¾ inch long at the tip of the stem, each cluster with 5 to 12 spikelets (flower clusters). The main cluster of spikelets is stalkless and hemispheric in outline, auxiliary clusters are on stalks ½ to about 3 inches long, with spikelets arranged widely spreading to ascending and the terminal spikelet usually erect. At the base of the group of clusters are 2 to 4 ascending to spreading leaf-like bracts, the largest up to about 6 inches long and nearly erect.

[close-up of spikelets] Spikelets are flattened, linear-oblong in outline, up to 15mm (½ inch) long, with 8 to 30 florets, each subtended by a scale. Florets have 2 or 3 stamens and a 2-parted style. Scales are 2.5 to 3mm long, lance-oval, blunt at the tip, greenish-white with reddish-brown to maroon along the edge often just at the tip end, with a green midrib. The scales are arranged ascending and tightly packed, overlapping on opposite sides of the central spikelet stalk (rachilla).

Leaves and stems: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of maturing plant] Leaves are basal and alternate, typically 1 to 3 per stem near the base, flat, 1 to 3mm wide, as long as or shorter than the flowering stem. Basal sheaths are brown to reddish-brown. Stems are multiple from the base, erect to prostrate, 3-sided and smooth. Plants form loose to dense clumps and often form dense colonies.

Fruit: Fruit type: seed without plume

[photo of spikelet, scales and achenes] The floral scales and achenes (seeds) drop off individually when mature, leaving the naked stalk behind. Achenes are 1 to 1.2mm long, brown, lens-shaped and generally oval-elliptic in outline.


Cyperus diandrus is found along lake and pond shores, wet meadows, and other low, seasonally wet areas. It is easily confused with the more common Cyperus bipartitus, which has clusters usually with 5 or fewer spikelets, floral scales that are maroon to reddish-brown except maybe along the edge, especially at the tip end, and the style is not persistent (see comparison photo below).

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More photos

Photos by K. Chayka taken in Anoka and Ramsey counties. Photos courtesy Peter M. Dziuk taken in Chisago and Itasca counties.


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