"Chinese Herbal Medicine: Materia Medica, Third Edition by Dan Bensky, Steven Clavey, Erich Stoger, and Andrew Gamble 2004":

According to Traditional Chinese/Korean Medicine, American Ginseng promotes Yin energy, cleans excess Yang in the body, calms the body. The reason it has been claimed that American ginseng promotes Yin (shadow, cold, negative, female) while East Asian ginseng promotes Yang (sunshine, hot, positive, male) is that, according to traditional Korean medicine, things living in cold places are strong in Yang and vice versa, so that the two are balanced. Chinese/Korean ginseng grows in northeast China and Korea, the coldest area known to many Koreans in traditional times. Thus, ginseng from there is supposed to be very Yang. Originally, American ginseng was imported into China via subtropical Guangzhou, the seaport next to Hong Kong, so Chinese doctors believed that American ginseng must be good for Yin, because it came from a hot area. However they did not know that American ginseng can only grow in temperate regions. Nonetheless the root is legitimately classified as more Yin because it generates fluids.