This study was carried out to obtain the basic information on the development of flower bud and to clarify the characteristics of flower organ and flowering in Korean ginseng (Panax ginseng) and American ginseng (Panax quinquefolium). The formation of flower bud in the dormancy bud of Korean ginseng was initiated about the middle of June and completed late in September. The ovary, style and anther of Panax ginseng, violet-stem and yellow-berry variants, were formed earlier than those of Panax quinquefolium. Panax ginseng, therefore, flowered earlier by one month in comparison with Panax quinquefolium. As for the effect of temperature on the flowering of ginseng, both species, Panax ginseng and Panax quinquefolium, grown at 20 $^{circ}C$ flowered earlier than those at 15 $^{circ}C$ and field conditions, but did not flower at 30 $^{circ}C$. Seed characters were better in Panax ginseng than in Panax quinquefolium and the amount of seeds showed the highly significant positive correlation coefficient with peduncle length in both Panax ginseng and Panax quinquefolium.