Cyperus schweinitzii Torrey 



SCHWEINTZ' FLATSEDGE 



Sedge Family (Cyperaceae) 



CONSERVATION STATUS 



U.S. Fish and Wildlife Service: None. 



Bureau of Land Management: Watch. 



Montana Natural Heritage Program: G5 SI; Demonstrably secure globally, but may be 

 critically imperiled in Montana where it is extremely rare. 



DESCRIPTION: Schweinitz flatsedge is a grass-like perennial with stems, 10-40 cm (4-16 in) 

 high, from short, irregularly swollen rhizomes. The are 1 -4 mm wide and located mostly near the 

 base. The inflorescence is subtended by 3-6 long leaf-like bracts, some wider than the leaves. The 

 inflorescence is made of up ascending clusters of flattened spikelets that are 5-25 mm long, borne on 

 very short to long stalks. Flowers consist of only a small pointed scale, ca. 3-4 mm long, subtending 

 3 stamens and an ovary. The seed is triangular in cross-section. Fruiting in late June-August. 



This is the only perennial CYPERUS in Montana, and the only one occurring in an upland habitat. 



GEOGRAPHICAL DISTRIBUTION 



Global distribution: Great Lakes, Midwest and Great Plains, with many outliers; from 

 Quebec to Alberta, south to New Jersey, Texas, and New Mexico (Great Plains Flora 

 Association 1986). 



Montana distribution: Scattered dune and 

 outcrop areas and possibly along major eastern 

 rivers; a total of six occurrences are now known 

 from Carter, Cascade, Custer, and Sheridan 

 counties. 



Carter County distribution: Prior to 1997, 

 Cyperus schweinitzii was known from one 

 population at Medicine Rocks State Park. In 

 1 997 two populations were found on BLM land 

 in the vicinities of Mill Iron and Pine Hill in the 

 north part of the county. 



Cyperus schweinitzii 

 Schweinitz' Flatsedge 



HABITAT: The species is restricted to sand dune habitats or colluvial slopes below eroding 

 sandstone outcrops. The Custer County occurrence is near the Yellowstone River possibly in 



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