Cyperus engelmannii

Cyperus engelmannii
Brome-Missisquoi, Québec, Canada (2 Sept)
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Clade: Commelinids
Order: Poales
Family: Cyperaceae
Genus: Cyperus
Species:
C. engelmannii
Binomial name
Cyperus engelmannii
Synonyms[2]
Homotypic synonyms
    • 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 tenuior Engelm.

Cyperus engelmannii, commonly known as Engelmann's flatsedge, is a species of flowering plant in the sedge family Cyperaceae. 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.

Description

Cyperus engelmannii is an annual sedge that stands 10–50 cm (4–20 in) tall. It has a few narrow leaves at the base of the plant, each leaf up to 30 cm (12 in) 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 20 flowers 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]

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 0.3–0.4 mm and 0.5–0.7 mm, 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]

Taxonomy

Cyperus engelmannii was named and described by the German physician Ernst Gottlieb von Steudel in 1854.[1] The specific epithet engelmannii honors the German-American botanist George Engelmann who collected its type specimen at Cahokia, near St. Louis, in 1845.[10] As of November 2025, the name Cyperus engelmannii Steud. is widely recognized,[2][6][8][11][12][13] but some authorities consider it to be a synonym of Cyperus odoratus L.[9][14][15]

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 engelmannii Steud.,[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 November 2025, it is reported from the following provinces and states:

In 1995, it was reported from Kentucky, Missouri, Ohio, Pennsylvania, and Tennessee,[28] but as of November 2025, its distribution in the southeastern United States is poorly known.[12]

Conservation

As of October 2025, 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 to vulnerable (S2S3) in Vermont,[27] and vulnerable (S3) in Delaware.[20] It is classified as a rare plant by the state of Pennsylvania.[26]

See also

References

  1. ^ a b "Cyperus engelmannii Steud.". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 23 October 2025.
  2. ^ a b c d "Cyperus engelmannii Steud.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 3 November 2025.
  3. ^ a b "Cyperus engelmannii (Engelmann's Flatsedge)". Minnesota Wildflowers. Retrieved 26 October 2025.
  4. ^ a b "Engelmann's Flatsedge". MassWildlife's Natural Heritage & Endangered Species Program. Commonwealth of Massachusetts. Retrieved 24 October 2025.
  5. ^ "Key to Cyperus". Flora of the Southeastern United States. Retrieved 22 October 2025.
  6. ^ a b Standley (2025).
  7. ^ Naczi (2017), p. 4.
  8. ^ a b Tucker & Gandhi (2019).
  9. ^ a b Tucker, Gordon C.; Marcks, Brian G.; Carter, J. Richard (2002). "Cyperus odoratus". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 23. New York and Oxford: Oxford University Press. Retrieved 26 October 2025 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  10. ^ "Specimen GH00027616 (isosyntype): Cyperus engelmannii Steudel". Harvard University Herbaria & Libraries. Retrieved 23 October 2025.
  11. ^ a b "Cyperus engelmannii Steudel". Database of Canadian Vascular Plants. Retrieved 26 October 2025.
  12. ^ a b "Cyperus engelmannii". Flora of the Southeastern United States. Retrieved 29 October 2025.
  13. ^ a b Reznicek, A. A.; Voss, E. G.; Walters, B. S. (February 2011). "Cyperus engelmannii Steud.". Michigan Flora Online. University of Michigan. Retrieved 26 October 2025.
  14. ^ NRCS. "Cyperus odoratus". PLANTS Database. United States Department of Agriculture (USDA). Retrieved 26 October 2025.
  15. ^ "Cyperus odoratus subsp. odoratus". World Flora Online. Retrieved 3 November 2025.
  16. ^ "Cyperus odoratus var. engelmannii (Steud.) R.Carter, S.D.Jones & Wipff". International Plant Names Index (IPNI). Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Botanic Gardens. Retrieved 30 October 2025.
  17. ^ a b "Cyperus odoratus L. var. engelmannii (Steud.) R.Carter, S.D.Jones & Wipff". Digital Atlas of the Virginia Flora. Retrieved 30 October 2025.
  18. ^ Tucker & Gandhi (2019), p. 356.
  19. ^ Naczi (2017), p. 9.
  20. ^ a b McAvoy, William A. (2024). "Rare and Uncommon Plants of Delaware" (PDF). Delaware Department of Natural Resources and Environmental Control. Retrieved 30 October 2025.
  21. ^ "Cyperus engelmannii". Indiana Plant Atlas. Retrieved 30 October 2025.
  22. ^ a b Cullina, Melissa Dow; Connolly, Bryan; Sorrie, Bruce; Somers, Paul. "The Vascular Plants of Massachusetts: A County Checklist. First Revision". Massachusetts Natural Heritage & Endangered Species Program. Retrieved 30 October 2025.
  23. ^ a b "List of Endangered Plant Species and Plant Species of Concern" (PDF). New Jersey Department of Environmental Protection. January 2024. Retrieved 30 October 2025.
  24. ^ "Cyperus engelmannii". New York Flora Atlas. Retrieved 30 October 2025.
  25. ^ "Engelmann's Flatsedge — Cyperus engelmannii Steudel". Vascular Plants of North Carolina. Retrieved 30 October 2025.
  26. ^ a b "Pennsylvania Rare". Pennsylvania Code. Retrieved 30 October 2025.
  27. ^ a b "Rare and Uncommon Native Vascular Plants of Vermont" (PDF). Vermont Natural Heritage Inventory. 10 June 2024. Retrieved 24 October 2025.
  28. ^ Mears & Libby (1995).

Bibliography

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