The Q&A Archives: Soil Additives that Change Hydrangea Color

Question: I have heard that there is a variable in the soil which will change the color of Hydrangea bushes. My greenhouse people argued whether it was lime or iron. Can you help? Thank you for your help. Carol Miller Pennsville, NJ

Answer: Yes, if you acidify the soil by adding sulfur and lowering the pH to below 5.0, hydrangea flowers tend to turn blue. If you raise the pH to around 6.5, they tend to turn pink. It is a function of aluminum availability at the different pH levels.

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