toothed flatsedge

Cyperus dentatus is a perennial, herbaceous sedge that persists via a creeping rhizome with small tubers terminating the branches of the rootstalk. Its inflorescence bears clusters of spikelets, each with numerous florets. Each floret is covered by a scale, which is a type of bract in sedges and grasses. In addition to spikelets, plants often produce vegetative propagules called bulblets. These are unlike spikelets in appearance, and therefore a plant with bulblets is distinctive and readily identified. In 1859, the American naturalist Henry David Thoreau referred to this species as bulblet sedge, describing it as "a plant and color looking toward autumn".

The first description of Cyperus dentatus was published in 1817. It was also described (in English) by the American botanist John Torrey in 1823, and again in 1836. Torrey described "this beautiful species" as follows:

Stem about one foot long, leafy at the base, leaves shorter than the stem Inflorescence is a compound umbel with 4–7 primary rays of unequal length Three (3) leaf-like bracts at the base of the inflorescence A cluster of 3–5 compressed spikelets terminates each secondary ray of the inflorescence Each spikelet has 6–30 florets covered by scales with acute tips (less than 90 degrees) A more detailed description was published in Flora of North America in 2002. Cyperus dentatus has stems 8–50 cm (3–20 in) long. …

Cyperus dentatus is native to southeastern Canada and eastern United States.

Canada: New Brunswick, Nova Scotia, Ontario, Quebec United States: Connecticut, Delaware, District of Columbia, Indiana, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Tennessee, Vermont, Virginia Plant specimens have been collected as far south as the coastal plain of Alabama, but some authorities claim the species has not naturalized there. Reports from the southern U.S. states of Georgia, South Carolina, and North Carolina may actually be based on Cyperus lecontei, not Cyperus dentatus. Cyperus dentatus prefers sandy or gravelly shorelines and coastlines. It is commonly found throughout the Atlantic coastal pine barrens, an ecoregion known for its sandy, nutrient-poor soil. One of the original specimens of Cyperus dentatus was collected in the New Jersey Pine Barrens in the early 19th century. In Virginia, its habitat is restricted to acidic sinkhole ponds in the Shenandoah Valley west of the Blue Ridge in Augusta County.

Cyperus dentatus is a flowering plant whose season runs from July to October. Flowering occurs during the months of July and August while fruiting occurs from August to October. It also reproduces asexually by means of bulblets, tubers, and rhizomes. Bulblets are often seen in the presence of fruits but it is not uncommon to find plants with bulblets only (no fruits), especially in September when bulblet production is at its peak. In Quebec and Vermont where the species is uncommon, populations that were unable to produce viable seed, instead produced bulblets that were successfully germinated in the laboratory.