How to Alkalize Hydrangeas


The hydrangea macrophylla, which is native to Korea and Japan, includes varieties such as Bigleaf, French, Lacecap, Mophead, Penny Mac and Hortensia. These shrub-like varieties, surrounded by large, serrated foliage, produce large, round bloom clusters in white, green, pink, purple or blue, depending on the soil that supports them. Modifying the pH level of the soil--making it more alkaline or more acidic--can alter the color of the bloom.

Step 1

Take soil samples from the planting location and have them tested by your local agricultural extension agency or other soil testing laboratory in the area. For the best growth, regardless of color, the soil pH should be between 5.5 and 7.0.

Step 2

Create pink blooms by increasing the alkalinity of the soil. At least four to six months before the blooming cycle begins, sprinkle 3 to 8 cups of dolomitic lime around the base of the hydrangea plant. Subsequent waterings will deliver the lime down into the root system to begin increasing the pH level.

Step 3

Apply dolomitic lime, at the same rate, two to three more times in the late fall and mid winter. For the best pink colors, the soil pH should be at a range of 7.0 to 7.5.

Step 4

Apply a phosphorous-rich fertilizer to hydrangea plants in order to prevent aluminum from entering the root system. Follow the manufacturer's directions with regard to application dosage and schedule.

Tips and Warnings

  • White hydrangeas cannot be altered to produce blue or pink blooms.

Things You'll Need

  • Dolomitic lime
  • 25-10-10 (high phosphorous) fertilizer


  • Vintage Gardens: Hydrangea Care, Culture and Historical Background
  • Changing the Color of Hydrangeas
  • Floridata: Hydrangea macrophylla

Who Can Help

  • Orchard Nursery of Lafayette: Hydrangea FAQs
Keywords: soil pH, changing hydrangea colors, hydrangea macrophylla

About this Author

Deborah Waltenburg has been a freelance writer since 2002. In addition to her work for Demand Studios, Waltenburg has written for websites such as Freelance Writerville and Constant Content, and has worked as a ghostwriter for travel/tourism websites and numerous financial/debt reduction blogs.