Cyperus bipartitus (Shining Flatsedge)

Plant Info
Also known as: Slender Flatsedge, Brook Nutsedge
Genus:Cyperus
Family:Cyperaceae (Sedge)
Life cycle:annual
Origin:native
Habitat:sun; moist sandy or gravelly soil; muddy shores, stream banks, wet meadows, swales, wet ditches
Fruiting season:August - October
Plant height:1 to 10 inches
Wetland Indicator Status:GP: FACW MW: OBL NCNE: FACW
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 clusters] 2 to 6 clusters up to ½ inch long at the tip of the stem, each cluster with 3 to 8 spikelets (flower clusters), usually 5 or less. 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 or 3 ascending to spreading leaf-like bracts, the largest up to about 4 inches long and nearly erect.

[close-up of spikelets] Spikelets are flattened, linear-oblong in outline, up to 18mm (.7 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 1.9 to 2.7mm long, lance-oval, blunt at the tip, rather shiny, reddish-brown to maroon at the base, often all the way to the edge except green at the tip end, 3-ribbed 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, V-shaped in cross-section, 1 to 2mm wide, mostly shorter than the flowering stem, and green to olive green. 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, scale and achenes] The floral scales and achenes (seeds) drop off individually when mature, leaving the naked stalk behind. Achenes are 1 to 1.5mm long, brown to blackish, lens-shaped and generally oval in outline.

Notes:

Cyperus bipartitus is one of the more common flatsedges in Minnesota, found along lake and pond shores, wet meadows, and other low, seasonally wet areas. It is easily confused with Cyperus diandrus, which has clusters usually with 6 or more spikelets, floral scales that are maroon to reddish-brown along the edges, especially at the tip end, and long, persistent styles (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 Anoka and Chisago counties. Photo courtesy Steve Eggers taken in Dakota County.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Mark K - Tower, MN - Eagles Nest 3 Lake
on: 2017-08-12 07:31:34

How do I keep it from taking over my lawn? I am trying to grow grass and this stuff is not very green.

Posted by: K. Chayka
on: 2017-08-12 08:25:15

Mark, assuming you have lakeshore property, Cyperus bipartitus is in its natural habitat. In this battle trying to undo what Mother Nature did by design, Mother Nature will prevail. Try to accept it.

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