A new and distinct cultivar of Hydrangea macrophylla (Thunb.) named “ originated as a controlled cross between varieties. The cultivar ‘BC7.3’ can be blue or red depending on the acidity of the soil and the presence of aluminum. The variety ‘BC7.3’ has relatively compact, attractive inflorescences with relatively small sepalous florets, distinct sepal pigmentation and good commercial characteristics. When grown in the presence of aluminum, the upperside of the sepals is primarily R.H.S. 94 A (violet-blue group) and 86 B (violet group), the underside of the sepals is R.H.S. 93 D (violet-blue group) and 86 C violet group).
