I have a Nikko hydrangea, planted a couple of months ago, that has grown quite a bit and looks very healthy. I purchased it from a nursery with one mophead already on it but it was still green. The mophead has also grown but hasn't colored at all.
Another mophead is forming but is white. Its planted in shade with patchy morning sunlight for a few hours and has been kept well-watered. My other hydrangeas (not Nikkos) are blooming away beautifully. Any guesses as to why the flowers aren't coloring?
-- Tara