Why aren't my hydrangeas changing color?
Written by
Nguyen Minh
Reviewed by
Prof. Martin Thorne, Ph.D.If your hydrangeas won't change colour, there are a few potential blockers. The most likely culprit is simply that you have a non-changer, such as a panicle or white hydrangea, planted. No soil chemistry adjustment is going to alter them; they're stuck in their original colour, as I discovered when I planted my first garden!
Wrong Variety
- Bigleaf and mountain hydrangeas only change color
- Panicle, oakleaf, and smooth types stay fixed
- White hydrangeas lack color-changing pigments genetically
Soil Imbalance
- Blue needs pH below 5.5 with aluminum present
- Pink requires pH above 6.5 without aluminum
- Test soil every 60 days for accurate readings
Water Issues
- Hard water minerals neutralize soil amendments
- Tap water raises pH sabotaging blue blooms
- Rainwater maintains acidity for consistent color
Soil chemistry errors are often the reason for failing to achieve the colour change. To produce blue blooms, you need sufficient soluble aluminium in an acid soil. Shoot for a 10-20 ppm concentration, and have your aluminum levels checked annually. My hydrangeas remained pink until I added aluminium sulphate!
Water quality is derailing the best gardeners. Tap water contains minerals and gradually raises the pH over time. Hard water forms white crusts on the soil and binds the aluminum. Use rain barrels for blue hydrangeas. My client doubled his success rate switching water sources!
Feeding times mistakes. Aluminum slows down the development of red in developing buds for six months. Amend color next spring. Treat the soil in the fall for it to bloom next year. I write down dates in a garden book.
How to fix non-changing hydrangeas: 1. Confirm if your variety is capable of changing color, as some are not. 2. Test soil pH and aluminum levels to determine that. 3. Switch to using well or rainwater. 5. Amend correctly (if necessary) seasonally to reflect your soil makeup. Over time, your flowers will take on the tint that is natural to them.
Read the full article: Soil pH for Hydrangeas: Color Control Guide
