Yes, the color of hydrangeas can be changed from pink to blue (not so easy to make it go from blue to pink).
I'm in the process of "encouraging" my MIL's hydrangeas to go BACK to blue, like they were last year, when they were planted. Right now, they're a rather sickly blue-ish white. First application of "stuff" was two weeks ago, so I'm still in the waiting period.
USDA Zone 9, Sunset Zone 17
edited to update link
Last edited by cynthia_h
on Fri Mar 13, 2009 5:21 pm, edited 1 time in total.