Retrorse Flatsedge

Cyperus retrorsus var. retrorsus None

Stephen M. Young

Monocotyledoneae (Monocots)
Cyperaceae (Sedge Family)
State Protection
Listed as Endangered by New York State: in imminent danger of extirpation in New York. For animals, taking, importation, transportation, or possession is prohibited, except under license or permit. For plants, removal or damage without the consent of the landowner is prohibited.
Federal Protection
Not Listed
State Conservation Status Rank
Critically Imperiled in New York - Especially vulnerable to disappearing from New York due to extreme rarity or other factors; typically 5 or fewer populations or locations in New York, very few individuals, very restricted range, very few remaining acres (or miles of stream), and/or very steep declines.
Global Conservation Status Rank
Secure globally - Both the species as a whole and the subspecies/variety are common in the world; widespread and abundant (but may be rare in some parts of its range).


Did you know?

The species name means "turned backward or downward" and refers to the perigynia of the spikelets that face downward when mature (Fernald 1950). A collection on Jones Beach Island in 2003 was the first time it had been seen on the island since 1935.

State Ranking Justification

There are three existing populations but there is no information on population size from any one of them. There are three additional populations known, from 1899, the 1930s, and 1976 that have not been resurveyed although habitat still exists. There are eight populations that are extirpated due to loss of habitat.

Short-term Trends

None of the known populations have been rechecked so there is no information on short-term trends.

Long-term Trends

This plant has apparently always been rare as there have never been more than 20 known populations in the state. Its population numbers have declined over the long term as many of its sites in the New York City area have been destroyed.

Conservation and Management


Directed disturbance from the overuse of beaches and nearby swales and saltmarshes threatens this plant as does the invasion of Phragmites.

Conservation Strategies and Management Practices

Beach and dune areas where it occurs should be protected from vehicle and human use. The Phragmites should be eliminated if it threatens populations.

Research Needs

Habitat preferences and reproduction success should be studied to understand how populations could be augmented at its present locations.



In New York this species has been collected from sandy coastal habitats including maritime dunes and the upper edges of a salt marsh. More information on the habitat requirements of this species in the state is needed (New York Natural Heritage Program 2010). Open woods and thickets in moist to dry, sandy soils (FNA 2002). Sandy barrens and coast (Gleason & Cronquist 1991).

Associated Ecological Communities

  • Maritime dunes (guide)
    A community dominated by grasses and low shrubs that occurs on active and stabilized dunes along the Atlantic coast. The composition and structure of the vegetation is variable depending on stability of the dunes, amounts of sand deposition and erosion, and distance from the ocean.
  • Maritime grassland* (guide)
    A grassland community that occurs on rolling outwash plains of the glaciated portion of the Atlantic coastal plain, near the ocean and within the influence of offshore winds and salt spray.
  • Maritime shrubland* (guide)
    A shrubland community that occurs on dry seaside bluffs and headlands that are exposed to offshore winds and salt spray.

* probable association but not confirmed.

Associated Species

  • Cyperus grayi (Gray's flat sedge)
  • Hudsonia tomentosa (beach-heather)
  • Lechea pulchella (Leggett's pinweed)
  • Oenothera biennis (common evening-primrose)
  • Opuntia humifusa (eastern prickly-pear)
  • Prunus maritima (beach plum)
  • Schizachyrium scoparium
  • Solidago sempervirens (northern seaside goldenrod)


New York State Distribution

This flatsedge is currently known from Queens and Suffolk counties. It was historically known from most of Long Island, Staten Island and Westchester County.

Global Distribution

This flatsedge occurs along the Atlantic and Gulf coastal plain from Massachusetts and New York to Florida. It is also common inland from Virginia to Missouri and Oklahoma south to Texas.

Identification Comments

General Description

Coast Flatsedge is a perennial, clump-forming, grass-like herb. Its stems are slender (up to 2 mm wide) 3-sided, or more or less rounded, and up to 50 cm tall. It has 3 to 6 V or W-shaped leaves that are 1.5 to 4 mm wide and up to 40 cm long. The infloresence consists of a single spike held on 4 to 8 rays (branches), up to 3.5 cm long, subtended by 4 to 6 ascending, rough-margined leafy bracts. There are 40 to 120 spikelets (each of 1 to 3 flowers) clustered into dense heads. The pistillate scales are persistent, appressed, straw-colored to brownish but green in the middle, with 3-4 ribs, and 1.8-2.5 mm long. The fruit are 3-sided, brown achenes 1.2 to 1.7 mm long (FNA 2002).

Identifying Characteristics

Distinguishing characteristics: perennial, ellipsoid-cylindric heads, lowest flowering scale 2-2.5 mm; stigmas three; achenes trigonous.

Best Life Stage for Proper Identification

Mature fruit are needed for positive identification.

Similar Species

Cyperus echinatus has similar 3-sided achenes and few-flowered, dense heads, but differs by having large pistillate scales (lowest scale 3.5 to 4.3 mm versus 2 to 2.5 mm for C. retrorsus) and rounder heads (C. retrorsus has ellipsoid heads) (Gleason and Cronquist 1991).

Best Time to See

Retrorse Flatsedge's fruit appears in late July and persists through October.

  • Fruiting

The time of year you would expect to find Retrorse Flatsedge fruiting in New York.

Retrorse Flatsedge Images


Retrorse Flatsedge
Cyperus retrorsus var. retrorsus None

  • Kingdom Plantae
    • Phylum Anthophyta
      • Class Monocotyledoneae (Monocots)
        • Order Cyperales
          • Family Cyperaceae (Sedge Family)

Additional Common Names

  • Cyperus
  • Flat Sedge

Additional Resources

Best Identification Reference

Flora of North America Editorial Committee. 2002. Flora of North America, North of Mexico. Volume 23. Magnoliophyta: Commelinidae (in part): Cyperaceae. Oxford University Press, New York. 608 pp.

Other References

Fernald, M. L. 1950. Gray's manual of botany. 8th edition. Corrected printing (1970). D. Van Nostrand Company, New York. 1632 pp.

Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York. 910 pp.

Holmgren, Noel. 1998. The Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York.

New York Natural Heritage Program. 2010. Biotics database. New York Natural Heritage Program. New York State Department of Environmental Conservation. Albany, NY.

New York Natural Heritage Program. 2024. New York Natural Heritage Program Databases. Albany, NY.

Weldy, T. and D. Werier. 2010. New York flora atlas. [S.M. Landry, K.N. Campbell, and L.D. Mabe (original application development), Florida Center for Community Design and Research University of South Florida]. New York Flora Association, Albany, New York

Zaremba, Robert E. 1991. Corrections to phenology list of April 9, 1991.


About This Guide

This guide was authored by: Stephen M. Young

Information for this guide was last updated on: April 18, 2019

Please cite this page as:
New York Natural Heritage Program. 2024. Online Conservation Guide for Cyperus retrorsus var. retrorsus. Available from: Accessed July 19, 2024.