redroot flatsedge

Cyperus erythrorhizos is an annual sedge with red fibrous roots. It grows to a maximum of 1 m (3 ft 3 in) in height but is usually quite a bit shorter. It may have a number of long, wispy leaves around the base of the plant. The inflorescence may contain one to several spikes, each spike containing 20 to over 100 spikelets. Each spikelet is light greenish brown to reddish brown and is made up of up to 30 bracted flowers. The fruit is a glossy achene about a millimetre long.

Cyperus erythrorhizos is native to North America, ranging from Canada to Mexico. It is most common in the United States. It was discovered in Vermont in 2014. In Canada, it occurs in British Columbia, Manitoba, Ontario, and Quebec. In Mexico, it was initially discovered in Baja California near the U.S. border based on a specimen collected in 1894. It was subsequently found in the state of Tabasco in southern Mexico. It is a plant of wet areas such as rivers and ditches, generally at low elevations. Its season runs from July to December.