You might be battling a high pH soil, in which case long term acidifying
would mean laying down powdered aluminum sulphate (I like straight iron
sulphate), along with an acidifying fertilizer like Espoma's Hollytone. The
coffee grounds can only help.

Dave

"Suzanne Couturiaux" wrote in message
...
I planted a couple Nikko blue hydrangeas two years ago, but the flowers
haven't been blue (they were more of a pinkish white). I watered them
with an aluminum sulfate solution this spring and last fall to try to
make the flowers blue this year. Now, I'm considering adding old coffee
grounds to the soil -- Will this counteract the aluminum sulfate, or
will it help to make the flowers blue?

Thanks in advance for any help you can provide.

Suzanne