Neutral soils (pH of 5.5 to 6.5) = purple blooms. Acidic soils (pH of 5.5 and lower) = blue blooms. Add lime to the soil for pink blooms; add aluminum sulfate for blue blooms. ... If you are dead set on your hydrangea being pink or blue, grow it in a container where you can easily control the soil pH.

How do I get my hydrangea to turn blue?

To encourage blue hydrangea flowers, grow the plant in soil that has a pH of 5.2-5.5. If your soil is more alkaline, you can lower the pH by applying Soil Acidifier at the rate specified on the package. Soil pH can also be lowered (more gradually) by applying an acidic organic mulch, such as pine needles or pine bark.

What color does lime make hydrangeas?

Increase the pH of your soil by adding lime to it in early spring or late fall to produce pink or red hydrangea blooms. While adding lime to potted hydrangeas may be simpler, you can also incorporate it in your garden soil to produce a bed of beautiful pink French hydrangeas.