How to Grow Blue, Pink or Lavender Hydrangeas
- 1). Test the soil where your hydrangea is planted to determine its pH level. Check with nurseries or your county cooperative extension office for information on soil testing.
- 2). Amend your soil with aluminum sulfate or sulfur if it is too alkaline and you want blue flowers. Hydrangeas will produce blue flowers when the pH is between 5 and 5.5; some garden soil will have this range naturally. If your soil does not, add the amendment when you see new growth starting on your hydrangea in the spring. The correct amount to add is based on the starting pH of your soil and the soil type; check with your extension office for details.
- 3). Add lime to raise the pH of your soil if it is too acidic and you want pink hydrangea blooms. The blooms will be naturally pink if your soil has a pH of 6.5 or higher. If not, add lime to the soil when new growth emerges in early spring. Check with your extension service for the proper type and amount of lime, based on your beginning soil pH and the type of soil you have.
- 4). Maintain a pH level between 5.5 and 6.5 if you want lavender or purple hydrangea flowers, recommends the United States National Arboretum. At this soil pH, your hydrangea may produce a mix of bluish and pinkish flowers.