Flora of North America species comparison

Balsamorhiza deltoidea varies in the crenation of the leaf margins. The variability may stem from an old hybridization with B. hookeri or other species of Balsamorhiza. Otherwise, B. deltoidea shows little significant variability except where it hybridizes with B. careyana in the narrows of the Columbia River Gorge.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

At one time or another, most species of subg. Balsamorhiza have been synonymized under B. hookeri. Nevertheless, a number of taxa are justifiably segregated as species by their morphologic differences and geographic restrictions. One might logically choose either of two taxonomies: recognizing only two species in the entire genus, one representing subg. Artorhiza and the other subg. Balsamorhiza, or recognizing each slightly differing population as a species. Either course results in an unsatisfactory classification. The present classification is a compromise. A knotty problem persists. A central cluster of populations from eastern Washington to southeastern California display a number of minor and locally discrete morphologies. They tend to be less isolated from each other than are the peripheral populations, although some tend to mimic the latter ones in one or more characteristics. Their evolutionary history may be involved with past hybridizations with each other or with species of subg. Artorhiza, gene drift, and polyploidy. At present, it appears impossible to reach a satisfactory classification.

(Discussion copyrighted by Flora of North America; reprinted with permission.)