How to grow pink hydrangeas?

To grow pink hydrangeas, the most critical factor is maintaining alkaline soil conditions.

Understanding Hydrangea Color and Soil pH

The vibrant color of many Hydrangea macrophylla (Bigleaf Hydrangea) and Hydrangea serrata (Mountain Hydrangea) blooms is directly influenced by the soil's pH level. This fascinating phenomenon means you can often manipulate the color of your hydrangeas by adjusting the acidity or alkalinity of their growing environment.

The Key to Pink Blooms: Alkaline Soil

For hydrangeas to display beautiful pink or even red hues, they require an alkaline soil environment.

• Alkaline soil, with a pH above 7.0, promotes pinks and reds. This means the soil needs to have a higher concentration of alkalinity, which allows the plant to absorb aluminum differently, leading to pink pigmentation.

Other Hydrangea Colors

Understanding the full spectrum of color changes related to pH helps in achieving specific desired shades:

• Blue or Lavender-Blue: Generally speaking, acidic soil, with a pH lower than 6.0, yields blue or lavender-blue hydrangea blooms. In acidic conditions, aluminum is more readily available for the plant to absorb, which is essential for blue coloration.
• Purple or Bluish-Pink: When the soil pH falls somewhere in the middle, between 6 and 7, the blooms turn purple or bluish-pink. This indicates a balance where some aluminum is available but not as abundantly as in highly acidic soil.

Practical Steps to Cultivate Pink Hydrangeas

Achieving and maintaining the ideal alkaline soil for pink hydrangeas involves a few key steps.

1. Test Your Soil pH

Before making any adjustments, it's crucial to know your current soil's pH level.

• Purchase a Soil Test Kit: These are readily available at garden centers and provide a good indication of your soil's pH.
• Professional Soil Analysis: For the most accurate results and detailed recommendations, consider sending a soil sample to a local extension office or a specialized lab.

2. Adjust Soil pH for Pink

Once you know your starting pH, you can begin to amend your soil. To encourage pink blooms, you need to raise your soil's pH to above 7.0, or maintain it if it's already alkaline.

• Increase Alkalinity: To make your soil more alkaline, common methods include adding liming agents such as:
  • Garden Lime (Calcium Carbonate): This is a slow-acting amendment that gradually raises soil pH.
  • Dolomitic Lime (Calcium Magnesium Carbonate): Similar to garden lime, it also provides magnesium.
  • Wood Ash: Can also be used, but in moderation, as it's potent.
• Application: Always follow product instructions for application rates, as too much lime can harm your plants. It's generally better to make gradual adjustments over time rather than a single large application. Re-test your soil periodically to monitor changes.
• Avoid Acidifying Agents: Steer clear of fertilizers high in phosphorus or those marketed for "acid-loving plants," as these can inadvertently lower your soil's pH.
• Contrast for Blue Blooms: While our focus is on pink, it's worth noting that if you wanted to lower your pH to achieve blue blooms, you would add garden sulfur or aluminum sulfate to your soil.

3. Ongoing Care and Considerations

Beyond initial pH adjustments, continuous care supports healthy hydrangea growth and vibrant pink blooms.

• Location: Plant hydrangeas in a spot that receives partial shade, especially protection from intense afternoon sun, which can scorch leaves and blooms.
• Watering: Hydrangeas are thirsty plants, requiring consistent moisture. Water deeply, especially during dry spells.
• Fertilization: Use a balanced fertilizer, or one slightly higher in phosphorus (the middle number in the N-P-K ratio), as phosphorus can help bind aluminum in the soil, further preventing blue coloration and promoting pink.

By focusing on maintaining an alkaline soil pH above 7.0, you can effectively encourage your hydrangeas to produce those beautiful pink and red flowers you desire.

Soil pH and Hydrangea Color Chart