|What do you add to the soil to change the color
of of a blue hydrangea to pinkish/purple?
|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. Since soil in the Pacific Northwest is on the acidic side, apply lime or superphosphate to the soil now and this summer's blooms should be pink.