Flower:

2 to 8 hemispheric to oval clusters up to ½ inch across at the tip of the stem, each cluster with 3 to 15 spikelets (flower clusters), occasionally more. The main cluster of spikelets is stalkless, auxiliary clusters are smaller and short-stalked. At the base of the group of clusters are 2 to 5 leaf-like bracts of varying lengths, the largest up to 8 inches long and erect, the others widely spreading.

Spikelets are flattened, oblong-elliptic in outline, up to 7mm (¼ inch) long, with 8 to 20 florets, each subtended by a scale. Florets have a single stamen and a 3-parted style. Scales are about 1mm long, the body lance-oval, usually dark purplish-brown, sometimes yellowish, with 3 ribs, the midrib green with a minute point at the tip (mucronate). The scales are arranged ascending and overlapping on opposite sides of the central spikelet stalk (rachilla).

Leaves and stems:

Leaves are basal and alternate but typically near the base, flat, up to 4 inches long, 1 to 4mm wide, and mostly shorter than the flowering stem. Basal sheaths are purple-tinged to deep purple. Stems are multiple from the base, erect to prostrate, 3-sided and smooth. Plants form loose to dense clumps with 3 to 20 stems in a clump.

Fruit:

The floral scales and achenes (seeds) drop off individually when mature, leaving the naked stalk behind. Achenes are nearly as long as the scale, light brown, 3-sided and generally elliptic in shape, tapering to a pointed tip, wedge-shaped at the base.

Notes:

Cyperus fuscus is a non-native flatsedge currently only known from a single location, on a sandbar along the Mississippi River in a Grand Rapids park, though it is not unreasonable to think it has traveled down the river to other, as yet undiscovered, locations. Native to temperate Europe and Asia, its usual habitat is the seasonally wet shores of ponds, lakes and river banks, emerging in mid to late summer when water levels drop. Its overall form is similar to both Cyperus acuminatus and Cyperus squarrosus, clump-forming with a few to several hemispheric to oval clusters of spikelets, but which have slightly to strongly to spreading tips on floral scales, which C. fuscus scales lack. The coloring of the scales may resemble Cyperus bipartitus and other native Cyperus species, which typically have more elongated clusters with spikelets more spread out along the cluster stalk, and are more reddish-purple or reddish-brown than dark purplish-brown.