Flora of North America species comparison

Varieties 2 (2 in the flora).

Because of variation in the degree of hairiness on branches and leaves, thickness of leaves, leaf shape, sizes of racemes and flowers, and colors of fruits, Prunus virginiana has been split into forms, varieties, and segregate species. When viewed on a continental scale, most of the key characteristics used to separate these taxa intergrade enough so as to be useless.

The most useful distinction is between chokecherries found east of the Rocky Mountains and those found from the mountains westward. They differ in leaf shape and raceme size; the variation is imperfectly correlated. The eastern plants generally have their larger leaves obovate with lengths less than two times widths, racemes typically less than 7 cm, and petals to 4 mm. Plants of the Rockies and west have longer racemes and larger petals, and generally their larger leaves are elliptic to oblanceolate leaves with lengths two or more times widths. Distinctions between the eastern and western varieties are least obvious from Montana to eastern Washington north into British Columbia, where the varietal ranges overlap. Plants of the High Plains show intergradation between those of the Rockies and those of the East. The taxonomic solution provided here is a single species of chokecherry in North America with an eastern and a western variety that overlap in range along a line from northeastern New Mexico to southwestern British Columbia.

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

Prunus subcordata shows variation in color, size, indument, and palatability of fruits, which has been the basis for recognition of taxonomic segregates. Variety kelloggii was described as a larger plant with less hairy foliage than in typical P. subcordata, and its fruits are yellow, larger, sweeter, and more pulpy. Variety rubicunda is a smaller shrub with bright red, bitter fruits. Most noteworthy is var. oregana with densely hairy ovaries and puberulent fruits, recorded only from the sparsely inhabited border region between northeastern California and adjacent Oregon. Specimens in herbaria are few and recent collections are lacking. The assignment of P. texana with hairy fruits to the plums (J. Shaw and R. L. Small 2005) makes this variant all the more interesting. Field study and collection followed by morphologic, genetic, and molecular study are needed to clarify its systematic position and significance.

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