Soil changes hydrangea’s color

One of my favorite flowering shrubs is the hydrangea. They are packed with color, and the recent varieties are very predictable bloomers. Many of the mature varieties bloom on last year’s growth only, and often a late freeze can destroy the buds that have already been set. Endless Summer and All Summer Beauty are two breakthrough varieties that produce flowers not only on last year’s growth, but also this year’s too!



It seems we always covet what we don’t have or can’t get, and blue hydrangeas migrate to that category. Our Hamilton County soil tends to eventually turn our fantastic blue hydrangeas to pink. That can be disappointing when a particular color palate was planned. But there is hope. Blue and pink hydrangeas can often be encouraged toward the other color with a little soil manipulation.

Changing pink to blue is not too difficult and can be accomplished by adding aluminum sulfate to the surrounding soil a few times a year. Mix a tablespoon of aluminum sulfate with one gallon of water and pour it around the hydrangea after saturating first. Couple with a high potassium fertilizer (25/5/30) and a healthy mulching for confident success in a few seasons. Sorry, no instant gratification here.

Blue to pink can be a little more challenging. Minimizing aluminum from the soil is the objective, and adding dolomitic lime two to three times a year to raise the ph level should do the trick. Use a 25/10/10 fertilizer with a high level of phosphorus.

White hydrangeas (Annabelle, White Dome, Tardiva, Oak Leafs) are meant to be white and are not prone to change.

While we love hydrangeas, their frustrating love affair with water is not terribly environmentally friendly. Plant them as specimens, instead of in mass, to control maintenance. My preference? Let the hydrangeas migrate to their eventual color and enjoy the process.