Ge-gen, a Chinese crude drug derived from the root of Pueraria lobata Ohwi of the family Leguminosae, is collected in the winter nowadays both in China and in Japan. However, in the old descriptions of materia medica written in ancient China, it was said that the proper collection season was May or in the early summer on Chinese calendar. Present herbological study resulted that the collection season had been changed in the Yuan or Ming dynasty in China, mainly because of the confusion with eating Ge-gen, which was collected in the winter. The Ge-gen collected in the early summer should be dispensed in the prescriptions written in the old medical books such as Shang-han-lun and Jin-kui-yao-lue.

In the previous paper, the authors have investigated a Chinese crude drug Ge-gen, the root of Pueraria species of the family Leguminosae, and concluded that it should be collected in the early summer for medical use. This is a report of the differences in the content of the constituents between Ge-gen harvested in the summer and in the winter. Yields of water extract of winter Ge-gens were generally higher, while no significant difference was recognized in the content of starch and flavonoids, such as puerarin and daidzin. Starch content varies widely with the stock, and that of the same stock did not show significant difference between the summer root and the winter one.