Flowering not very sensitive to late frosts, reblooming, from pale pink (neutral soils) to pale blue (acid soils).
Compact plant, adapted to semi-shaded areas remaining wet in summer.
Close to Hydrangea macrophylla, Hydrangea serrata are native to mountain areas of Japan, so are more hardy. 'Blue Bird' forms many flat inflorescences, type "Lacecap", with small dark blue central fertile flowers surrounded by large sterile flowers, light blue in acidic soil.