Hydrangeas, pink and blue

Our blushing Hydrangeas

By Amy McDowell

A Hydrangea’s color is as changeable as a chameleon. You may buy a Hydrangea with sky-blue blooms at the garden center that turns to pink in your garden. It’s a frustrating trait for gardeners intent on designing with a particular color. The Hydrangeas, though, are simply responding to their environment. A low soil pH (acidic) will turn Hydrangeas blue and a high soil pH (alkaline) will turn them pink.

Virtually all of the soils in central Iowa are alkaline. Areas where fallen oak leaves or evergreen needles collect and decay may be more neutral, but it’s unlikely that you’ll find any acidic soils with a pH lower than six in this area. And that means no blue Hydrangeas for our gardens. Plant a blue and it will convert to pink. (The whites stay white regardless of pH.)

Even if you go crazy mulching with pine needles or pouring on Miracid or Aluminum Sulfate, the plant’s response will be both mild and temporary. Not only are our soils alkaline, but our tap water is, too. A blue Hydrangea grown in a controlled environment like a pot is likely to turn pink eventually just because of the water.

So pink or white it is. At least we’ve got choices of bush, tree or climbing Hydrangeas. We can decorate our gardens with mopheads like Annabelle, lacecaps like Radiata, repeat bloomers like Endless Summer and White Moth and ornamental trees like Pee Gee and Pink Diamond. We’ve also got the white lacecap climbing Hydrangea and the deep burgundy fall color of the oakleaf Hydrangea.

Variations in bloom and foliage are ever expanding. Although its not hardy here, the new “Lady in Red” Hydrangea (zones 6-9) is red stemmed and red veined. It’s just a matter of time before hybridizers create something like that for our colder winters.

Don’t be blue when your Hydrangea blushes pink. We all must adapt to our environment.