Cyperus odoratus
Cyperus odoratus is a species of flowering plant in the sedge family Cyperaceae. It is known by the common names fragrant flatsedge and rusty flatsedge. It has a pantropical distribution that extends into the temperate regions of North and South America. The species is quite variable and may in fact be more than one species included under a single name.
Description
Cyperus odoratus sensu lato is an annual sedge approaching half a meter in height on average but known to grow much taller. It usually has some long, thin leaves around the base of the plant. The inflorescence is made up of one to several cylindrical spikes, each resembling a bottle brush. There are 5 to 8 leaf-like bracts at the base of the inflorescence. Each of the spikes bears a large number of flat, oval-shaped spikelets. Each spikelet is usually light brown to reddish-brown and has a few to over 20 flowers. Each flower is covered by a tough, flat scale with a visible midvein. The fruit is a flat achene less than two millimeters long.Cyperus odoratus sensu stricto is similar to Cyperus engelmannii. The floral scales of Cyperus odoratus are overlapping. In contrast, the mature floral scales of Cyperus engelmannii do not overlap, that is, the tip of each scale does not reach the base of the next scale on the same side of the spikelet. The mature achenes of Cyperus odoratus are slightly ellipsoid, while those of Cyperus engelmannii are narrow with linear edges. The widths of fully developed achenes are 0.5–0.7 mm and 0.3–0.4 mm, respectively.
Cyperus odoratus and Cyperus engelmannii are the only two Cyperus species in temperate North America with spikelets that eventually break into one-seeded segments. At maturity, each spikelet breaks into segments each consisting of a scale and an achene held together by a portion of the floral axis.
Taxonomy
Cyperus odoratus was first described by the Swedish botanist Carl Linnaeus in 1753. Linnaeus based his diagnosis on a specimen collected along a riverbank in North America., the following infraspecific names are accepted by both Plants of the World Online and World Flora Online:Cyperus odoratus subsp. odoratusCyperus odoratus subsp. transcaucasicus
The typical subspecies Cyperus odoratus subsp. odoratus has dozens of synonyms. Cyperus odoratus var. engelmannii is a homotypic synonym of Cyperus engelmannii
Cyperus odoratus is a member of Cyperus subgen. Diclidium. It is one of two species in subgenus Diclidium whose range extends into temperate North America.