Bigleaf Hydrangea

Bigleaf hydrangea (Hydrangea macrophylla, Hydrangeaceae) is a fast-growing deciduous shrub from Japan (possibly Korea), reaching about 4 feet tall and 9 feet wide with a mounding form. The signature feature is pH-dependent flower color: acidic soil produces blue flowers and alkaline soil produces pink, with white cultivars unaffected. Flowers appear in mophead (spherical) or lacecap (flat-topped) forms from July to August.

Bigleaf hydrangea grows in part shade on adaptable soils (pH 4.5 to 8.0) with moderate water needs, hardy in Zones 5b to 8b. It blooms on old wood; prune after flowering. Disease pressure is notable, with 13 documented associations. Root weevil and foliar nematode are the primary pests. Hundreds of cultivars are in the trade spanning both mophead and lacecap forms. Powdery mildew-susceptible cultivars include 'Nikko Blue,' 'Forever Pink,' and 'Madame Emile Mouilliere.'