Prairie burnet

Poterium annuum Nuttall in W. J. Hooker, Fl. Bor.-Amer. 1: 198. 1832; Sanguisorba annua (Nuttall) Nuttall

Plants winter-annual or biennial, glabrous; taproots 1–4(–6) dm. Stamens (2 or)4. Fruits: hypanthia ridges extended into thin wings, ˂0.5 mm wide˃; sepals tuberculose-thickened proximally.

Flowering Mar–Jun; fruiting Apr–Jul. Sandy and rocky soil, prairies, oak savannas, oak woodlands, disturbed areas (pastures, roadsides), often locally moister sites; 0–500 m; Ont.; Ark., Iowa, Kans., N.Y., Okla., S.C., Tex.

The eastern records (Ontario, Iowa, Massachusetts, New York, and South Carolina) all appear to represent adventives or non-persistent waifs. A record from Maryland (J. B. S. Norton and R. G. Brown 1946) is plausible; no specimen is known to the author.