How to Use Lime to Make Pink Hydrangeas

Blue hydrangeas need aluminum to keep their color, so if you want pink flowers, you'll need to keep the mineral away from your plants' roots. You do that by adding lime to soil to raise the pH balance. The easiest approach is to work with potted plants, but you can add lime to regular garden soil as well.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Soil testing kit
• Gardening lime (sold in garden stores and home improvement centers)
• Garden soil
• Hydrangea plants
• Rake or spade
• Drop or broadcast spreader (optional)
• Gardening gloves, face mask and eye protection

Preparation

1. Get your soil's pH level tested to know how much lime you need. Contact your local university extension service, or purchase a test kit at a home improvement center or garden store. To get hydrangeas pink, shoot for a soil pH of about 6.5 to 7.0. Any higher and your soil will be too alkaline for anything to grow.

2. Decide how much lime you need based on the tests and the condition of your soil. You may have to experiment, especially if you have particularly sandy or clay soil. As rule of thumb, use about 2 to 5 lbs. per 100 square feet. For a few medium-sized plants, use about 2 to 4 tbsp. per plant.

3. Purchase lime at a local home improvement center or garden store. Lime isn't a big seller, so it can be hard to find. You can get it in a 5 lb. bag, which should be enough for a medium-sized garden.

4. Wait until fall to add lime to soil, to give it plenty of time to break down before the spring growing season.

5. Make sure the soil is dry when you add lime, and allow winter snows and rain to work it deep into the soil.

Application

6. Sprinkle the measured amount of lime around the root base of established plants, being careful not to spill it on the leaves or branches. Use a spade or rake to work it into the soil as best you can without disturbing the roots. You'll get the best results in a bare garden before you set plants by using a drop or broadcast spreader. Then rake the lime into the soil.

7. Wait at least a few weeks--or until spring--before fertilizing the soil. Commercial fertilizers can adversely affect lime application.

8. Set plants in spring, unless you're working with established hydrangeas.

9. Check the colors once your plant blooms. If you still haven't achieved the pink hue you want, add more lime to the soil in spring or summer. Lime isn't terribly soluble, so water thoroughly throughout the growing season to work the additional lime into the soil.

10. Continue to add lime to the soil about once every two years to keep your plants in the pink.

Tips & Warnings

• If your blue hydrangeas won't turn pink no matter how much lime you add, it may be because you live in an area with high rainfall, which creates highly acidic soil conditions. Consider growing hydrangeas in pots to really control the pH balance and color.
• Adding lime to your soil changes the pH balance, so be sure your hydrangeas aren't sharing soil with plants that need lots of acid.
• Lime is a safe substance, but pouring it can create a dust cloud, so wear gardening gloves, a mask and eye protection.
• Always follow directions on the lime packaging.
• White hydrangeas will not turn color no matter how many amendments you add to the soil.
• Don't go above a pH balance of 7.0, as this can harm surrounding plants.

References

• University of Rhode Island Landscape Horticulture Program: Hydrangeas Fact Sheet
• Clemson University Cooperative Extension: Changing the pH of Your Soil
• East Texas Gardening: Hydrangeas-Popular Plants for the South

Resources

• Hydrangeas! Hydrangeas!
• West Virginia University Extension Service: Liming the Lawn