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.)

The name Prunus serrulata has been widely applied to P. speciosa by North American botanists and horticulturalists (for example, P. G. Russell 1934; A. J. Rehder 1940); some Japanese cherry experts now circumscribe P. serrulata more narrowly so that it includes only the white-petaled, double-flowered cultivars closely resembling the nomenclatural type. The single-flowered plants that are found escaping rarely and perhaps naturalizing in the flora area have been called P. lannesiana (Carrière) E. H. Wilson forma albida (Makino) E. H. Wilson or P. speciosa. Based on principal components analysis of 35 morphological characters from 468 individuals of the P. serrulata complex and related taxa, K. S. Chang et al. (2007) argued that forma albida is distinctive and separated from other taxa of the P. serrulata complex. H. Ohba (2001) recognized it at species rank as Cerasus speciosa (Koidzumi) H. Ohba. The classification and nomenclature of Japanese flowering cherries are complex, convoluted, and subject to varying interpretations, and no attempt is made to resolve them here. Centuries of selection and hybridization have blurred species distinctions, and it may be best to do as horticulturalists have and forsake botanical species names in favor of traditional and cultivar names. Whatever the name, these Japanese flowering cherries are widely grown as ornamentals where winters are not too cold nor summers too hot; they escape only rarely and have been found naturalizing only near planted specimens.

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