Answer: Pink and red hydrangeas often turn blue or purple in acid soils. Blue hydrangeas can turn pink in alkaline soils. Plants can be made (or kept) blue by applying aluminum sulfate to the soil; plants can be kept pink by liming the soil or applying superphosphate. Some hydrangeas will remain either pink or blue regardless of the soil pH so the answer to your question really depends upon the cultvar. If you provide the name of the hydrangea we will be able to guide you as to what soil conditions it will require for the desired color.
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