By Paul Epsom
"By Paul Epsom from The Victory Garden
Posted on July 23, 2010
Today we're talking about hydrangeas. One very popular problem with hydrangea flowers is not having them turn blue.
As you may know, there are many species of hydrangea. A very common species is the Hydrangea Macrophylla, the big leaf hydrangeas with the massive mophead flowers. These come in shades of red, white, pink and blue.
And if your blue hydrangeas are not turning blue it is probably a problem of soil acidity. The more alkaline in the soil the less blue the flowers become. You need to make the soil slightly more acidic to have the flower develop more of that desirable deep blue color.
Turning the soil more acidic is actually more difficult than turning it alkaline. One solution is to add sulfur to the soil—an aluminum sulfate or iron sulfate. Peat moss or even pin needles are naturally acidic so you can try adding some of those too.
The best way for making a soil acidic is to mix in one of those rhododendron or camellia fertilizers back when you start gardening in the spring. There are lots of these fertilizers out there.
No, one word of caution—do read the instructions. It's easy to over fertilize—thinking that is going to make the flowers bluer and bluer—but too much fertilizer and acid can damage the plant.