Coefficient of Conservatism:
Coefficient of Wetness:
A. A. Reznicek
Although weedy in habit, considered native and known from Michigan as early as 1838 (Cass Co.). By the 1880’s, documented from Detroit, Wayne Co. to Keweenaw Co. Favored habitats include roadsides, railroads, fields, farmyards, cultivated ground, logged areas, and other disturbed sites; also in oak savanna, on stream banks and even floodplains, rocky ground.
Plants can be quite large (even to 1 m tall) and bushy, whereas in A. psilostachya they are usually little if at all branched. The fruits have a ring of well-developed thorn-like protuberances below the base of the beak.
Besides the hybrid with A. psilostachya mentioned under that species, a much less common hybrid with A. trifida is known, A. ×helenae Rouleau. This has been recognized thus far in Michigan only in Cheboygan, Hillsdale, and Washtenaw Cos.