Hydrangeas & Coffee Grounds – Adding coffee grounds or other organic material to your hydrangea’s soil will reduce the pH level and make aluminum more available to the plant. The result will be hydrangeas that are blue in color.
French Hydrangea: Blue or Pink Blooms? Your hydrangea is simply responding to the soil pH. Blue flowers are produced in acid soil (pH and lower), and pink flowers are produced in alkaline soil (pH 7 and higher). You can add aluminum sulfate around your