How Do I Turn My Hydrangea Blue?
It is important to note that only bigleaf hydrangeas can turn blue. Attempting to turn any hydrangea blue that isn’t supposed to will just cause frustration.
The color of the plant is determined by the amount of aluminum available to the plant. In many cases the aluminum is already present but simply bound up in the soil. In order to free up the aluminum, you must make the soil acidic (lower pH).
It is very helpful to know your current soil pH, and a soil test will tell you what it is. In southeast Michigan much of our soil has a higher pH and will create beautiful pink hydrangea flowers.
The ideal pH for your soil will be 5.2 – 5.5 for blue hydrangeas. Several products can help to lower your pH including aluminum sulfate, garden sulfur, coffee grounds, aged grass clippings, pine bark mulch and garden compost. It is recommended to try one of these and test your soil again to determine how well your application worked. Plants in the ground can be hard to maintain a low pH around so view this as a journey and not a destination.