Description

Potentially Misidentified Species- At least 14 Cyperus sp.are known from intertidal areas of Chesapeake Bay. Several other introduced species in the watershed include C. fuscus (Brown Flatsedge), C. iria (Ricefield Flatsedge), and C. rotundus (Purple nutsedge) from nontidal wetlands and uplands.

Common Names- The last name is Australian. Many other foreign names are not given here (Holm et al. 1977).

Taxonomy

Kingdom	Phylum	Class	Order	Family	Genus
Plantae	Magnoliophyta	Liliopsida	Cyperales	Cyperaceae	Cyperus

Synonyms

Invasion History

Chesapeake Bay Status

First Record	Population	Range	Introduction	Residency	Source Region	Native Region	Vectors
1934	Established	Expanding	Introduced	Regular Resident	East Asia	East Asia	Agriculture(Packing Material

History of Spread

Cyperus difformis (Variable Flatsedge) is native to the Old World, and is widespread in East Asia and also in Africa. It is now widely scattered in temperate North America including the southeast United States and California. Its present range includes southern Europe, Asia, Central America, Mexico, South America, Australia, and the Pacific Islands. It is known as a weed in 46 countries, primarily affecting rice fields (Holm et al. 1977).

Cyperus difformis was found among herbarium specimens collected in MD before 1753 (Brown et al. 1987). No further records are known from North America until a collection in Sonora, Mexico, in 1851. Lipscomb (1980) suggests the occurrence of at least five separate introductions of C. difformis to North America. The first United States collection (excluding the one in colonial MD) was in 1915, in CA (Lipscomb 1980). The start of the present invasion of the southeastern US may have been indicated by a collection in Owl Creek, Viriginia Beach VA (near Rudee's inlet) (Fernald 1935). However, no more southeast United States records were reported until 1974, from Currituck Sound NC (Tyndall 1983). Records of C. difformis are now widely scattered over the Southeast, populations, with populations in NC, TN, MS, and LA (Tyndall 1983); and also in AL, FL, PA, TX, KY. Much of the spread appears to be occurring along major waterways (Bryson and Carter 1994; Mears and Libby 1995). Occurrences have also been noted to the north of Chesapeake Bay in PA (Rhoads and Klein 1993) and at Sandy Hook NJ (Stalter et al. 2000).

The first definite Chesapeake Bay region record (excluding the isolated Colonial MD specimen) was at Owl Creek, Virginia Beach VA (Fernald 1935), near Rudee's Inlet. It was not found by Tyndall at same site in 1978, and was presumed extinct near Virginia Beach, where the site was greatly altered by development (Tyndall 1983). In 1979, it was collected in Dyke Marsh, Potomac River, Alexandria VA (U.S. National Herbarium Collection), and found again, more recently, by Strong and Shetler (Strong 1995). Steury (2004) reported 'hundreds of plants' in 'wet ground' in Kenilworth Park adjacent to the Anacostia River. Harvill et al.'s (1992) map shows records in 5 tidewater counties and one interior VA county.

History References - Brown et al. 1987; Bryson and Carter 1994; Fernald 1935; Harvill et al. 1992; Holm et al. 1977; Lipscomb 1980; Mears and Libby 1995; Rhoads and Klein 1993; Stalter et al. 2000; Steury 2004; Tyndall 1983; U.S. National Herbarium Collection

Invasion Comments

First Record - An herbarium specimen of Cyperus difformis, from MD, was collected before 1753 (Brown et al. 1987), but there were no further records from North America until 1851, and none from the Chesapeake region until 1934 (Lipscomb 1980). The 1753 record is considered to represent an early, failed invasion.

Likely Vectors of Introduction - Fernald (1935) suggested that Cyperus difformis was introduced with rice straw used in packing Fernald (1935). Alternatively, it could have been introduced by bird or ship dispersal from established populations in Mexico (Lipscomb 1980).

Ecology

Environmental Tolerances

	For Survival		For Reproduction
	Minimum	Maximum	Minimum	Maximum
Temperature (ºC)
Salinity (‰)	0.0		0.0
Oxygen
pH
	Salinity Range	fresh-meso

Age and Growth

	Male	Female
Minimum Adult Size (mm)	100.0	100.0
Typical Adult Size (mm)	425.0	425.0
Maximum Adult Size (mm)	750.0	750.0
Maximum Longevity (yrs)
Typical Longevity (yrs

Reproduction

	Start	Peak	End
Reproductive Season
Typical Number of Young Per Reproductive Event
Sexuality Mode(s)
Mode(s) of Asexual Reproduction
Fertilization Type(s)
More than One Reproduction Event per Year
Reproductive Startegy
Egg/Seed Form

Impacts

Economic Impacts in Chesapeake Bay

Cyperus difformis (Variable Flatsedge) is very rare and sporadic, though apparently increasing in abundance around Chesapeake Bay (Harvill et al. 1986; Harvill et al. 1992; Tyndall 1983). References- Harvill et al. 1986; Harvill et al. 1992; Tyndall 1983

Economic Impacts Outside of Chesapeake Bay

Cyperus difformis (Variable Flatsedge) is a major weed of rice in CA (Lipscomb 1980) and worldwide, and is included in the book 'The World's Worst Weeds' (Holm et al. 1977). It is spreading in the southeastern United States, with no impacts reported yet in MS, but population size has increased 200-400-fold in MS from 1991 to 1994 (Bryson and Carter 1994).

References - Bryson and Carter 1994; Holm et al. 1977; Lipscomb 1980

Ecological Impacts on Chesapeake Native Species

Cyperus difformis (Variable Flatsedge) is an aggressive weed in disturbed warm, moist regions worldwide (Holm et al. 1977), and is spreading in the southeast United States (Bryson and Carter 1994; Mears and Libby 1995; Tyndall 1983). However, it is rare in Chesapeake Bay region, where it is near the northern limit of its range (Harvill et al. 1992; Tyndall 1983).

References - Bryson and Carter 1994; Harvill et al. 1992; Holm et al. 1977; Mears and Libby 1995; Tyndall 1983

Ecological Impacts on Other Chesapeake Non-Native Species

Cyperus difformis (Variable Flatsedge) is a fiercely competitive weed with rice and other crops of warm, moist regions worldwide (Holm et al. 1977), spreading in the southeast United States (Bryson and Carter 1994; Mears and Libby 1995; Tyndall 1983), but rare in Chesapeake Bay, near the northern limit of its range (Harvill et al. 1992;Tyndall 1983). Competition with introduced plants such as Kyllinga gracillima (Pasture Flatsedge) is possible, but has not been documented.

References - Bryson and Carter 1994; Harvill et al. 1992; Holm et al. 1977; Mears and Libby 1995; Tyndall 1983

References

Brown, Melvin L.; Reveal, J. L; Broome, C. R.; Frick, George F. (1987) Comments on the vegetation of colonial Maryland, Huntia 7: 247-283

Bryson, Charles T.; Carter, Richard (1994) Notes on Carex, Cyperus, and Kyllinga (Cyperaceae) in Mississippi with records of eight species previously unreported to the state, Sida 16: 171-182

Fernald, M. L. (1935) Midsummer vascular plants of southeastern Virginia, Rhodora 37: 378-454

Fernald, Merritt L. (1950) Gray's Manual of Botany, In: (Eds.) . , New York. Pp.

Gleason, Henry A.; Cronquist, Arthur (1991) Manual of vascular plants of northeastern United States and adjacent Canada, In: (Eds.) . , Bronx, New York. Pp.

Harvill, A. M., Jr.; Bradley, T. R.; Stevens, C. E.; Weiboldt, T.F.; Ware, D.E.; Ogle, D. W. (1986) Atlas of the Virginia Flora, , Farmville, VA. Pp.

Harvill, A. M.; Bradley, Ted R.; Stevens, Charles E.; Wieboldt, Thomas F.; Ware, Donna M. E.; Ogle, Douglas W.; Ramsey, Gwynn W.; Fleming, Gary P. (1992) Atlas of the Virginia Flora, , Burkeville, VA. Pp.

Holm, Leroy G.; Plucknett, Donald L.; Pancho, Juan V.; Herberger, James P. (1977) The World's Worst Weeds - Distribution and Biology., In: (Eds.) . , Honolulu. Pp.

Kartesz, John T. (1994) A synonymized checklist of the vascular flora of the United States, Canada, and Greenland., In: (Eds.) . , Portland OR. Pp.

Krauss, R.W.; Brown, R. G.; Rappleye, R. D.; Owens, A. B.; Shearer, C.; Hsiao, E.; Reveal, J. (1971) Checklist of plant species occurring within the hightide limits of the Chesapeake Bay, and its tributaries., , College Park, Maryland. Pp.

Lipscomb, Barney L. (1980) Cyperus difformis L. (Cyperaceae) in North America, Sida 8: 320-327

Mears, Randy L.; Libby, Garry (1995) New records of Cyperus from Kentucky, Castanea 60: 79-82

Resource Management Inc. (1993) National list of plant species that occur in wetlands., , Minneapolis.. Pp.

Rhoads, Ann Fowler; Klein, William McKinley, Jr. (1993) The Plants of Pennsylvania, , Philadelphia. Pp.

Stalter, Richard; Lamont, Eric E. (2000) Vascular flora of Sandy Hook, New Jersey, Bartonia 60: 105-116

1995 Introduced plants in the Chesapeake Bay region, conversation with Paul Fofonoff.

Tyndall, R. Wayne (1983) Distribution of Cyperus difformis L. (Cyperaceae) in the Southeastern United States, Castanea 48: 277-280