"Yakushima-ajisai" (Hydrangea grosseserrata) belongs to the Hydrangeaceae (the Hydrangea family). It is a small deciduous tree that is distributed the Yakushima Island and the Ryukyu Islands. This tree grows in forests along streams, and can reach about 1 m in height. The trunk is much branced and the young branches are reddish brown. The leaves are oblong to oblong-lanceolate, opposite, with caudate apexes and coarsely acute serrated on the upper part of edges. The flowers bloom in terminal cymes from May to June. The flowers consists of pale yellow, many amphoteric flowers and yellowish white 2 to 4 decorative flowers. There are 4 to 5 petaloid sepals, and there are irregular serrated teeth on the rim.