
Hydrangeas were so much more predictable only a few decades ago. They were either colored or white. White was obviously white. In the Santa Clara Valley, colored was pink. We knew them as colored only because they technically had potential to be blue, whether or not we actually saw it. Application of aluminum sulfate was necessary for blue floral color. Such color was only temporary, and could fade in the process of bloom if the dosage of aluminum sulfate was inadequate. Consequently, blue hydrangeas were rare. However, within the redwood forests of the Santa Cruz Mountains to the south and west of the Santa Clara Valley, most colored hydrangeas were blue. Application of lime was necessary to make them pink. Just like blue floral color within the Santa Clara Valley, pink floral color within the redwood forests was only temporary, and could fade in the process of bloom if the dosage of lime was inadequate. Nowadays modern hydrangeas are not so sensitive to soil pH. Blue hydrangeas bloom a bit more purplish in the Santa Clara Valley, but are still mostly blue. Pink hydrangeas likewise bloom a bit more purplish in the Santa Cruz Mountains, but are still mostly pink.
What ever happened to the formerly common white hydrangea? It used to one of the three standard types of hydrangea; and the other two were really variants of the same sorts of ‘pink or blue’ hydrangea that I wrote about in ‘
There are so many more of the fancier cultivars of hydrangea, Hydrangea macrophylla, than there were as recently as the 1990s. Many of the pink and blue hydrangeas were interchangeable years ago. They would bloom blue if the soil was acidic. They would bloom pink if the soil was alkaline. Their color changed accordingly when planted from potting media into soil of another pH.