Cyperus × nieuwlandii Geise
Family: Cyperaceae
Hybrid Flatsedge
Cyperus × nieuwlandii image
From Flora of Indiana (1940) by Charles C. Deam

This hybrid was described by Geise (Amer. Midland Nat. 15: 245-246. 1934). She reports three specimens collected by Nieuwland in the vicinity of Chain Lakes in St. Joseph County. I have seen these specimens and their determination seems to be correct.