I have nikko blue hydrangea 8 yrs. old. the 1st yr. they were blue. Now they are pink and lavender and have been since. I feed them acidic fertilizer. I have talked with the nursery man and he told me my water is probably neutral. Is there anything now this fall I can do to help them to come back to blue. I cannot change the ph of the water. Pls. help if you can and many, many Thanks.
Nikko Blue Hydrangeas
Certified GKH Gardening Expert
It can be difficult to get soil down to a low enough (acidic) pH to get hydrangeas to really turn blue. Aluminum is also needed in the soil for the plant to create the blue color. Having a soil pH test done can show you how close you are to the necessary pH of 5.2-5.5.
Aluminum sulfate can help with both the pH and the aluminum requirement: