Flowers of Thermopsis
rhombifolia are similar to those of Thermopsis
divaricarpa. The species are distinguished by the shape of the seed pods.
T. rhombifolia has strongly curved pods, while T.
divaricarpa has spreading, slightly curved seed pods. T. rhombifolia
is found primarily on the plains and lower foothills. T.
on the foothills and mountains.
Some sources consider T.
rhombifolia, T. divaricarpa and T. montana to be varieties
of a single species.