The mystery of hydrangea colors has intrigued gardeners for ages. The changing nature of hydrangea color often seems magical especially when last year's fabulous royal blue blossoms turn into purplish-red the next year. I wondered if I understand why color changes, could I actually produce the colors that I wanted. Here's what I found out.
Soil Controls Color
First thing to know is that it is not possible to change the color of hydrangeas that are naturally white. Most of the 70-75 species of hydrangea are in this category. To get those spectacular red, blue, and shades of pink and purple turn to the Hydrangea macrophylla, the common "mop-head" type of plant.