 Formerly, two subspecies of the plains garter snake were widely recognized, but most authorities have since dropped recognition of them.The first, "T. r. radix", was commonly referred to as the eastern plains garter snake, while "T. r. haydeni" (Kennicott, 1860) was commonly referred to as the western plains garter snake.However, the distinction between the two of them is weak, partly based on the number of scales and partly on slight coloration differences, with "T. r. haydeni" said to have cleaner markings and more ventral and neck scales.