Hydrangeas, always a favorite for garden enthusiasts, are unique in that the color of their flowers change dramatically.  First, let’s clarify that the hydrangea in question are the hydrangea macrophylia, often called Mophead due to their large rounded blooms.  These are the “bush form” hydrangea, as opposed to tree form, which typically have white to light green blooms.  The most common variety of Mophead hydrangea, Endless Summer, is easily found in local nurseries and is the most popular due to the claim that the plant will continuously bloom all season.  There is a second hydrangea macrophylia, Lacecaps that stay white.   The color question is likely the most frequent query addressed to the gardeners from Terrapin Landscapes.  The question typically revolves around the fact that the blooms are a vibrant blue upon purchase, but it’s often noted that they start to turn pink as the plant gets older.  So why the color change, and what can be done about it? Hardy in zones 6 through 10, hydrangeas tend to be a bit fussy about where they live.  The color is in the soil.  So, what is it that allows us, as gardeners, to alter the color of our Hydrangea...