Coefficient of Conservatism:
Coefficient of Wetness:
A. A. Reznicek
Considered a native species, typical of river floodplains, but weedy in habit. In richer, moister soil than our other species, including moist ground near lakes and streams, fens, meadows; roadsides, farmyards, gardens, alleys, vacant lots, and other disturbed sites. Collected by the First Survey in 1837 (St. Joseph Co.), but the relative recent date of many collections, especially in the Upper Peninsula, suggests considerable expansion of range in historic time.
Plants 2 m tall are not unusual; our other two species never come close to such a height. The fruiting involucres are ca. 6–11 mm long, including a short beak below which are several stout, short, thorn-like protuberances. In our other species, the fruits are less than 5 mm long.