Photo: Flowers of hydrangea in my home
Hydrangea ( Hortensia) is native in Japan. Flowers are produced
from May to June. A variety of types, or cultivars, are grown in
Japan island. The colour of flowers are white, blue, pink or
purples. → http://en.wikipedia.org/wiki/Hydrangea
Dr. Siebold named one cultivar as Hydrangea otakusa Siebold et
Zuccani. " otakusa " mean Otaki, who was Japanese wife of Dr.
Von Siebold. Von Siebold used to call his wife "Otakusa" and
named a Hydrangea after her.
→ http://en.wikipedia.org/wiki/Philipp_Franz_von_Siebold