Coefficient of Conservatism:
Coefficient of Wetness:
Known in Michigan only from wet ground (marsh, streamside, muddy hollow) at Isle Royale.
Occasionally plants of R. pensylvanicus with larger flowers than usual might appear similar to this species, but their cylindrical heads of achenes in contrast to the thick-ovoid ones of R. macounii are quite different. The achene beak in R. macounii may be strongly turned toward one edge, but sometimes it is as short and straight, as in some specimens of R. pensylvanicus. The sepals in both species usually become strongly reflexed.