Moist thickets, shores, beach flats, marshes, fens, wet meadows, conifer swamps (cedar or tamarack), stream and river banks, ditches and swales, borders of forests.

Variable in size and shape of leaflets and stipules, in pubescence, and in other characters. The several named varieties, however, seem to run into each other. One of the clearest is var. myrtifolius (Willd.) A. Gray, with the stem wingless. Other forms have the stem narrowly winged, and it is mostly among these plants that rare ones occur with stipules more than 7 mm broad. These can usually also be distinguished from the wingless L. ochroleucus by their bluish to pink or purple flowers (except in albinos) and the often ± sharply acute basal lobes on the stipules (compared to rather rounded, though toothed, lobes in L. ochroleucus). This is a species that may repay further study.