Answer: Hydrangeas grow best in rich, loose soil, in sites that get morning sun and afternoon shade. The flowers can change from blue to pink (or pink to blue) because of soil acidity or alkalinity. Blue flowers result from acidic soils; pink flowers result from alkaline soils; white flowers won't change color regardless of soil pH. For the blue plant, add 4 tablespoons of aluminum sulfate to a gallon of water and apply to the soil. Do this again in 3-4 weeks. For the pink hydranges, sprinkle 3 cups of lime on the soil beneath the plants. The color change takes time but if you treat them annually they should keep the right colors.
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