Flora of North America species comparison

In Arizona, var. blumeriana is known from Cochise, Pima, and Santa Cruz counties.

Numerous varieties have been described among populations of the widespread and erratically variable Crotalaria sagittalis, but neither D. Isely (1998) nor D. R. Windler (1974) recognized varieties, noting that further study was necessary to understand the variation patterns, especially among the Mexican populations. However, Isely observed that isolated Arizona populations of var. blumeriana have small pods (7–15 mm), and the often tiny plants, which may be either erect or decumbent, are not the same as those found in the eastern United States. In contrast, garden plants grown from seeds of representative plants of var. blumeriana were as large as any of the plants grown from field seed of typical Mexican C. sagittalis (Windler 1973). The type specimen of C. pringlei is more like typical C. sagittalis and is unusual among the Arizona populations.

Variety blumeriana is treated formally here, recognizing that it is far out of range, geographically and ecologically, from typical Crotalaria sagittalis of the eastern United States. Its evolutionary affinities, perhaps, are with Mexican populations, but almost all of the species in Mexico occur in the southern half of the country, disjunct from both the Arizona and eastern North American plants.

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