Pediomelum esculentum

Pediomelum esculentum, synonym Psoralea esculenta, common name prairie turnip or timpsila, is an herbaceous perennial plant native to prairies and dry woodlands of central North America, which bears a starchy tuberous root edible as a root vegetable. English names for the plant include tipsin, teepsenee, breadroot, breadroot scurf pea, large Indian breadroot, prairie potato and pomme blanche. The prairie turnip continues to be a staple food of the Plains Indians. A related species, Pediomelum hypogaeum (syn. Psoralea hypogaea), the little breadroot, is also edible, although the plant and root are smaller. Another species, Pediomelum argophyllum (syn. Psoralea argophylla), was probably harvested for food only in times of famine....read more on Wikipedia.