Cyperus ferax var. engelmannii(Steud.) Kük. ex Osten
Cyperus ferax subsp. engelmannii(Steud.) Kük.
Cyperus odoratus var. engelmannii(Steud.) R.Carter, S.D.Jones & Wipff
Heterotypic synonyms
Cyperus tenuiorEngelm.
Cyperus engelmannii, commonly known as Engelmann's flatsedge, is a species of flowering plant in the sedge familyCyperaceae. It is native to North America but the full extent of its range is not well understood. The name honors the German-American botanist George Engelmann who collected its type specimen near St. Louis in 1845. It is similar in appearance to Cyperus odoratus and the name is considered by some to be a synonym for the latter.
Cyperus engelmannii is an annualsedge that stands 10–50cm (4–20in) tall. It has a few narrow leaves at the base of the plant, each leaf up to 30cm (12in) long. The inflorescence consists of several cylindrical spikes, each resembling a bottle brush. Typically there are several leaf-like bracts at the base of the inflorescence. Each spike bears dozens of spikelets arranged bottle-brush fashion along its axis. Each spikelet, only slightly flattened and nearly cylindrical, supports up to 20flowers arranged in two vertical rows along the floral axis (called the rachilla). Each of the small, inconspicuous flowers is subtended by a scale (a kind of bract). The fruit is a three-sided achene.[3][4]
With floral scales that do not overlap
Cyperus engelmannii is similar to Cyperus odoratus. At maturity, the 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. In contrast, the floral scales of Cyperus odoratus are overlapping throughout the season. The mature achenes of Cyperus engelmannii are narrow with linear (parallel) edges, while those of Cyperus odoratus are slightly ellipsoid.[5][6] The widths of fully developed achenes are 0.3–0.4mm and 0.5–0.7mm, respectively.[7]
Cyperus engelmannii and Cyperus odoratus are the only two Cyperus species in temperate North America with spikelets that eventually break into one-seeded segments.[8] At maturity, each spikelet breaks into segments each consisting of a scale and an achene held together by a portion of the rachilla.[9]
Cyperus odoratus var.engelmannii was named and described by Carter et al.in 1996.[16] Most authorities consider Cyperus odoratus var.engelmannii(Steud.) R.Carter, S.D.Jones & Wipff to be a homotypic synonym of Cyperus engelmanniiSteud.,[2] but some accept the variety, not the species.[17]
Cyperus engelmannii is a member of Cyperus subgen.Diclidium(Schrad.ex Nees) C.B.Clarke.[18] It is one of two species in subgenus Diclidium whose range extends into temperate North America (the other being Cyperus odoratus).
Distribution and habitat
Cyperus engelmannii is native to North America.[2] In the United States, it ranges from Massachusetts to Minnesota, southward to Virginia and Missouri, but the full extent of its range in North America is not known.[19]As of November2025[update], it is reported from the following provinces and states:
United States: Delaware,[20] Indiana,[21] Massachusetts,[22] Michigan,[13] Minnesota,[3] New Jersey,[23] New York,[24] North Carolina,[25] Pennsylvania,[26] Vermont,[27] Virginia[17]
In 1995, it was reported from Kentucky, Missouri, Ohio, Pennsylvania, and Tennessee,[28] but as of November2025[update], its distribution in the southeastern United States is poorly known.[12]
Conservation
As of October2025[update], Cyperus engelmannii is a threatened species of greatest conservation need in Massachusetts.[4] It is imperiled (S2) in Massachusetts and New Jersey,[22][23] imperiled-vulnerable (S2S3) in Vermont,[27] and vulnerable (S3) in Delaware.[20] It is classified as a rare plant by the state of Pennsylvania.[26]
1 2 Reznicek, A. A.; Voss, E. G.; Walters, B. S. (February 2011). "Cyperus engelmanniiSteud.". Michigan Flora Online. University of Michigan. Retrieved 26 October 2025.
1 2 McAvoy, William A. (2024). "Rare and Uncommon Plants of Delaware"(PDF). Delaware Department of Natural Resources and Environmental Control. Retrieved 30 October 2025.
Mears, Randy L.; Libby, Gary W. (March 1995). "New Records of Cyperus (Cyperaceae) from Kentucky". Castanea. 60 (1): 79–82. JSTOR4033838.
Naczi, R.F.C. (2017). "Portion of Cyperaceae, the sedge family: Cyperus". In Naczi, R.F.C.; Abbott, J.R.; and collaborators (eds.). New Manual of Vascular Plants of Northeastern United States and Adjacent Canada, compiled in 2016, 2017. Bronx, NY: New York Botanical Garden Press.
Standley, Lisa A. (2025). "Cyperus engelmannii in New England". Rhodora. 126 (1006): 178–182. doi:10.3119/25-08.
Tucker, Gordon C.; Gandhi, Kanchi N. (2019). "Nomenclatural notes on Cyperus odoratus and related species (Cyperaceae)". Harvard Papers in Botany. 24 (2): 349–357. doi:10.3100/hpib.v24iss2.2019.n18. ISSN1938-2944.
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