Why do my Hydrangea flowers change colors?
We often get the question about Hydrangea flower color when someone purchases a red flowering Hydrangea and the flower fades to purple.
Soils are usually the key ingredient to flower color in Hydrangeas. Soil acidity or alkalinity will change the color of Hydrangea blooms. You can change the color back by treating the soil.
Pink and red Hydrangeas often turn blue or purple in acid soils. Hydrangeas can be made red again by liming the soil or applying super phosphate. To keep the blue color, treat the soil with 2 Tablespoons of aluminum sulphate per plant, making 4 to 6 applications at 2 week intervals.
Start treating in the spring before the plant begins to bloom. For pink flowers, add lime to the soil. It may take a couple of years to balance your soil out and keep the Hydrangeas the color you desire.