Question
We were told to either prune hydrangeas after flowering or not at all, but considering ours flower all summer (zone 4) when is the best time to prune.  I like to cut the blossoms to have for vases, etc.

Answer
Jim,

It depends on what kind of hydrangea you have.  

Grandiflora, PeeGee, and Annebelle hydrangea bloom on new growth so these would be pruned in early spring before flowering.

Oakleaf, bigleaf, nikko blue bloom on year old growth.  These would be pruned after flowering.  

Good luck

Gary