# How to Change Hydrangea Colors: Complete Guide
One of the most magical aspects of growing hydrangeas is the ability to change their bloom colors. Unlike most flowers, bigleaf hydrangeas (Hydrangea macrophylla) act as natural pH indicators, shifting between blue, pink, and purple based on soil chemistry.
## Which Hydrangeas Change Color?
Not all hydrangeas can change color:
- **Bigleaf (H. macrophylla)**: Changes color - mophead and lacecap types
- **Oakleaf (H. quercifolia)**: Always white, aging to pink
- **Panicle (H. paniculata)**: White to pink, not pH-dependent
- **Smooth (H. arborescens)**: Always white
- **Climbing (H. anomala)**: Always white
## The Science Behind Color Change
The color shift depends on **aluminum availability** in the soil, which is controlled by pH:
| Soil pH | Aluminum Available | Bloom Color |
|---------|-------------------|-------------|
| 5.0-5.5 | High | Deep Blue |
| 5.5-6.0 | Moderate | Blue to Purple |
| 6.0-6.5 | Low | Purple to Pink |
| 6.5-7.0 | Very Low | Pink |
| 7.0+ | None | Deep Pink |
## Making Hydrangeas Blue
To achieve blue blooms, you need **acidic soil (pH 5.0-5.5)** and available aluminum:
### Step-by-Step Process
1. **Test your soil pH** with a reliable kit
2. **Lower pH** if above 5.5 using aluminum sulfate or elemental sulfur
3. **Water with rain water** (tap water is often alkaline)
4. **Re-test monthly** and adjust gradually
5. **Wait 2-3 months** for visible color changes
## Making Hydrangeas Pink
For pink blooms, you need **alkaline soil (pH 6.5-7.0)** that locks up aluminum:
1. **Test your soil pH**
2. **Raise pH** using garden lime or dolomitic lime
3. **Avoid aluminum-containing fertilizers**
4. **Use phosphorus-rich fertilizer** (phosphorus binds aluminum)
5. **Wait 2-3 months** for color changes
## Common Mistakes to Avoid
1. **Changing pH too quickly** - can damage roots
2. **Using vinegar** - temporary fix, harms soil biology
3. **Ignoring variety genetics** - some cultivars resist change
4. **Over-applying aluminum sulfate** - toxic at high levels
5. **Not testing soil first** - guessing wastes time and money
## FAQ
**Q: How long does color change take?**
A: 2-6 months depending on starting pH and method used.
**Q: Can I change color mid-season?**
A: It's possible but best to start in early spring before buds form.
## Conclusion
Changing hydrangea colors is a rewarding gardening project that combines science with art. Start with a soil test, make gradual adjustments, and be patient.
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