ydrangeas can be found in white, pink, purple and blue — and shades in between. But where do those colors come from? Underground, in the soil. Depending on its pH, the soil will tell you if your flowers will be blue, pink, purple or other variations. And there are ways to change the color of your hydrangea if you are hoping for a deep pink or bright blue.
“It’s not hard; the problem is you have to do it early in the season,” Lisa Bartlett of the American Hydrangea Society, which is based in Atlanta. The organization has about 350 members.
“You do it when the buds are super tight and when they are forming,” she said. “To make them blue it’s aluminum sulfate, and to make them pink it’s lime.”
Aluminum sulfate comes in powdered and liquid forms, although Bartless said it’s the liquid form that’s easier for the plant to pick up.
Blue hydrangeas come from soil with a low pH, ranging from about 4.5 to 5.5. Purple grows in about 5.5 to 6.5, and pink can be found in a pH of 6.0 to 7.0. So, blue hydrangeas grow in a highly acid soil and pink hydrangeas are produced in a neutral or slightly acid soil.
“I just think it’s one of those very comfortable plants that remind us of being with our grandparents, being with our mothers,” she said. “It’s the first plant people see in a landscape, I think. It’s a nice, sweet plant.”
“If you want a purple hydrangea there are cultivars that are reliably purple,” Bartlett said. “Merrit supreme, is probably one of my top five favorite hydrangeas. It is dark and intensely purple, has excellent dark green foliage, really a beautiful, strong plant.
To get this blue color, aluminum must be available to the hydrangea. The pH of the soil needs to be low and typically adding aluminum sulfate will lower the pH of the soil. Another way to lower the pH is to add organic matter like coffee grounds, fruit and vegetable peels and grass clippings, according to www.hydrangeashydrangeas.com.
Adding lime several times will help produce a pink hydrangea. According to www.flowersandbulbs.com, a pH of about 6.0 to 6.2 will produce a nice pink, but if you go above 6.4 your plant may have an iron deficiency.
The beautiful white hydrangeas’ color cannot be changed.
“They are just white hydrangeas,” Bartlett said. “This is going to be one of the best seasons for hydrangea,” Bartlett said. “It was a nice steady cold this winter, one of the best seasons I’ve ever seen.”
For more information about hydrangea colors, visit www.americanhydrangeasociety.org.
Ashley Bates and Scott Rogers are staff members of The Gainesville Times, a sister paper of The Covington News that is published daily. They may be reached at email@example.com or srogers@gainesville-