Hydrangea Color and pH Hydrangea Biochemistry – pH, Aluminum, and Bigleaf Hydrangea Flower Color Did you know that our beauty queen hydrangea, Hydrangea macrophylla, combats aluminum toxicity with its flowers? Same for H. serrata (mountain hydranga) and Dichroa febrifuga (evergreen hydrangea), but they're not in the magazines (dare I say, garden tabloids?) as much. It’s well known that pH influences flower color on bigleaf and mountain hydrangeas, but how this happens is even more interesting than pH alone. Her...