|The cultivar 'Diadem' is a deciduous, upright shrub with slender stems and pointed, 6 inch long, ovate leaves, which are much more narrow than its Bigleaf Hydrangea relatives. Foliage turns red in fall.
H. serrata have flowers that are held in rounded, 2 to 4 inch wide, lacy corymbs and borne from summer to fall. Native to Korea and Japan.
Hydrangea serrata and its cultivars are also sometimes listed as H. macrophylla subsp. serrata. 'Bluebird' is also sometimes listed as 'Acuminata'.