The same thing happened to me but then I found out you are not supposed
to cut backt the woody stems each year. Are you cutting back the woody
stems at the end of the season or in the beginning of spring? If so
don't. When the leaves fall off in the winter just let new leaves come
out of the old stems in the spring and you will get flowers.

TFD

brsher wrote:
Can anyone suggest a reason my hydrangas won't flower? They are on a
Northern exposure, and are tall and green.
The first few years I got a lot of flowers. Since then, almost nothing.