There are a few different methods you can use to change the color of your hydrangeas from pink or blue to white. The color of hydrangeas is affected by the pH level of the soil. Blue and purple hydrangeas grow in acidic soil with a pH of 5.2-5.5. Pink and red hydrangeas grow in neutral to alkaline soil with a pH of 6.0-6.2. To make hydrangeas turn white, you need to make the soil more alkaline by raising the pH to 6.5-7.0.
What causes hydrangea flowers to be pink or blue?
The pigments in hydrangea flowers are affected by the availability of aluminum in the soil. In acidic soils, aluminum is more available to the plant. The aluminum reacts with the pigments in the flowers and turns them blue. In neutral or alkaline soils, aluminum is tied up and unavailable to the plant. Without aluminum, the flowers turn pink or red.
How do I make my soil more alkaline to turn flowers white?
Here are some methods to make your hydrangea soil more alkaline:
- Add lime – Lime raises pH. Add pelletized dolomitic limestone by following package instructions.
- Use aluminum sulfate – This ties up aluminum in the soil. Follow package directions.
- Water with baking soda – Dissolve 1 tsp baking soda per gallon of water and use to water plants.
- Mulch with lime – Add a 2-3 inch layer of lime around the plant.
- Plant in already alkaline soil – Choose a planting spot with alkaline soil.
When should I add amendments to change the pH?
The best times to add soil amendments like lime or aluminum sulfate are:
- Fall – This gives the amendment time to change the pH before spring growth.
- Early spring – But not too early, wait until the ground thaws.
- After blooming – You’ll see results next season.
Avoid making major changes right before or during flowering. It takes time for pH changes to take effect.
How much should I add to change the pH?
Follow package instructions when adding soil amendments like lime or aluminum sulfate. As a general guideline for established bushes:
- Lime – Add 1/2 to 1 cup per plant, depending on bush size.
- Aluminum sulfate – Use 1-2 tsp per foot of shrub height.
Test your soil pH before and after making changes to determine the right amount for your soil.
When will I see results?
It takes time for pH changes to reach all areas of the soil. Here’s a general timeline:
- 1-2 months – You may see some color change in this time.
- 3-6 months – More significant color change as pH change spreads.
- 12+ months – Full color change throughout the plant.
Be patient, it can take over a year to see the full impact of pH changes on flower color.
Can I still get blue or pink flowers?
Yes! If you want to switch back to pink or blue flowers in the future:
- For blue – Lower the pH by applying sulfur or acidic fertilizer.
- For pink – Maintain a neutral pH around 6.5-7.0.
It is possible to have a hydrangea with different colored flowers by maintaining optimal pH levels in separate areas of the root zone.
What type of hydrangea do I have?
The main types of hydrangeas are:
| Type | Description |
|---|---|
| Bigleaf (macrophylla) | Large, round flower heads. Most common. Blue or pink flowers. |
| Oakleaf (quercifolia) | Cone-shaped flowers. Leaves shaped like oak leaves. White flowers. |
| Panicle (paniculata) | Cone-shaped flowers. Upright, loose clusters. White or pink flowers. |
| Smooth (arborescens) | Dome-shaped flowers. White or green flowers. |
Knowing the type of hydrangea you have will help determine the best way to alter the flower color.
Should I prune my hydrangeas?
Pruning can be done to shape the plant but should be avoided before color change is desired. Pruning removes some of the buds that will produce the flowers. But don’t worry about removing spent blooms – that won’t affect next year’s flowers.
If pruning is needed, do it immediately after flowering. Avoid heavy pruning that removes much of the plant. Take out only crossing, damaged or dead branches.
Will changing the pH affect the health of my hydrangeas?
With proper application of soil amendments, changing the pH should not negatively affect the health of established plants. They are adaptable to a wide pH range. Problems are more likely if drastic changes occur rapidly. Introduce pH changes slowly and test regularly.
Young or transplanted hydrangeas may be more sensitive to pH fluctuations. Wait to alter pH until they are settled and growing well.
Do I need to fertilize for vibrant white blooms?
Fertilizer is not necessary to change hydrangea color but can promote growth and flowering. Use one with more phosphorus than nitrogen. Suggested ratios:
- 10-20-10
- 15-30-15
A balanced, all-purpose fertilizer like 10-10-10 is also fine. Apply in early spring using the rates on the packaging.
Will changing flower color affect winter hardiness?
Changing the pH to make flowers turn white should not make hydrangeas less hardy in winter. Some tips for winter prep:
- Wait to prune until stems are dead – Usually March or April.
- Wrap or insulate container plants.
- Add extra mulch around the base.
- Avoid fertilizer after mid-August.
Select cold hardy hydrangea species and cultivars for colder regions. Oakleaf and smooth hydrangeas are quite hardy.
Conclusion
Turning hydrangea flowers white requires raising the pH of the soil to make it more alkaline. This can be done by adding lime, using aluminum sulfate, and other methods. Give soil amendments time to work throughout the soil for best results. Test soil regularly, fertilize lightly in spring, and take winter protection measures. With proper care, you can enjoy vibrant white hydrangea blooms.
