Hydrangea serrata Ser. var.yezoensis (Koidz.) H. Ohba

in Japan, Honshu,Teradomari, June 2010 (pictures 1 to 5)
in Japan, Honshu, Road to Niigata, June 2010 (picture 6)

Description in Prodr. (DC.) 4: 15 (1830)