Hydrangeas come in shades of blue, pink or white. White stays white but pink flowers can be made blue or blue flowers can be made pink by changing the acidity of the soil. In neutral to alkaline soil(over pH 7) the flower becomes pink (or even red), in a strong acid soil (below pH 5.5) the flower becomes blue.
Due to a lack of acidity the beautiful blue hydrangea may take a disappointing pinkish hue over time. Since the flower buds are formed on old wood the secret to maintaining or returning to an intense beautiful blue is application of
Master Nursery Hydra Blue (aluminum sulfate) to acidify the soil. Two or three applications may be necessary.
To alter color intensity to blue, use
Master Nursery's Hydra Blue. This is accomplished by mixing 4 tablespoons to a gallon of water and applying to the base of the plant. Four to Six months before blooming begins as these processes take time.