The "Yama-ajisai" (Hydrangea serrata) belongs to Hydrangeaceae (the Hydrangea family). It is a small deciduous tree that is native westward from Honshu to Shikoku, Kyushu of Japan, and the southern Korean Peninsula. This tree grows in woodland edges or along mountain streams and can reach 1-1.5 m in height. The leaves are thin, oblong and opposite. The corymbs are borne on the new branches, and the pale purple bisexualflowers at center and the neuter flowers at around the periphery bloom from June to August. The neuter flower is a calyx and it has various colors, white, pale rose-pink or blue.