I'm a hydrangea hoarder. There, I said it. So when I bought a hydrangea from craigslist 2 years ago and it wasnt blooming, I was a sad panda. I fertilized it with fish fertilizer, I dug it up and moved it, Made sure it was facing East, I pruned it properly, Sang some Peter Cetera to her...NOTHING. Not a single bud.
So last week, I took some used coffee grounds and scattered it at the roots, I did quite a bit ( probably 4 cups worth )
And I kid you not, a week later, the entire plant was bursting with buds.
I nearly cried. Nearly.
I've always known that you can change the color of your hydrangeas ( most of the time ) by changing the PH of your soil ( I threw ash on mine last year and they went from purple to mauvey pink mix mid summer ) and knew that coffee grounds were good for them after they bloom, but never thought to do it before.