Coefficient of Conservatism:
Coefficient of Wetness:
A Eurasian species; in disturbed ground in Michigan but perhaps not persisting. Collected by J. W. Robbins on the Keweenaw Peninsula in 1863 (GH, MICH), and by O. A. Farwell at Detroit (Wayne Co.) in 1894 (1460, BLH).
Even in a narrower sense than the original breadth assigned to it by Linnaeus, this is an extremely variable species. The fruit is glabrous, strongly spiraled. A collection from a farm at Grand Rapids (Kent Co.) in 1902 (E. J. Cole, MICH, ALBC) appears to be M. minima (L.) L., with fruit ± pubescent between the spines and weakly glandular on the surface; unlike in M. polymorpha, the stipules are at most shallowly toothed at the base; the stem is pubescent. Its status in 1902 is not clear, whether cultivated or a waif from contaminated seed. The corolla in both these species is slightly longer than in M. lupulina, but distinctly smaller than in M. sativa.