As far as sedges go, Carex is the most diverse genus. Being able to recognize groups or sections of the genus that have similar characteristics is often a very helpful tool because it allows you to narrow down your species options substantially. Some of the other more species rich genera in the family Cyperaceae include Scirpus, Eleocharis, and Cyperus. In the genus Cyperus, the flowers are perfect and there are no perigynia (paper-like sacs surrounding the female flowers) as there are in the genus Carex. The scales subtending the flowers in Cyperus are folded in half, not flat or rounded as they are in many other genera. Morphologically, the genus that looks most similar to Cyperus in the United States is Dulichium. The flowers on plants in the genus Cyperus lack the long persistent styles (the tubercles) that are present in flowers on plants in the genus Dulichium, and Dulichium has axillary inflorescences whereas Cyperus has terminal inflorescences.
Within the genus Cyperus, as within the genus Carex, the species can be organized into several natural groups (subgenera) that share morphological characteristics. Within subgenus Cyperus, which has flowers with three stigmas (as opposed to two), spikelets along a conspicuous rachis (as opposed to being in digitate or glomerulate heads), and rachilla (the axis to which the flowers are attached) that disconnect from the rachis (the axis to which the spikelets attach) only at the base (as opposed to having rachilla that disconnect beneath each scale), two of the most commonly confused species in the Great Lakes region are Cyperus esculentus and Cyperus strigosus. Cyperus odoratus is also often confused with these two species, but it is taxonomically placed into subgenus Diclidium because the rachilla disconnect beneath each scale, not at the base of the spikelet. If you pull on a spikelet of a species in subgenus Diclidium from the end of the spikelet, the spikelet will break somewhere in the middle; pulling on a spikelet of a species in subgenus Cyperus from the end of the spikelet will result in the entire spikelet being removed from the rachis in an intact unit.
|Cyperus esculentus inflorescence and leaves|
|Cyperus strigosus inflorescence|
|Cyperus esculentus spikelet|
|Cyperus strigosus spikelet|
|Base and roots of Cyperus esculentus|
|Base and roots of Cyperus strigosus|