Last year I bought a number of Hydrangea plants from a nursery. They had been cut back and did not have any flowers. This year I got a great number of strong branches (tall and a lot of leaves) but only a few flowers. I don't know wether to cut them back or just leave them alone. Please can you advise me?
Many hydrangeas bloom on "old wood." That means they are forming their blossoms for next year and by cutting off branches, you are cutting off next year's flowers. Some bloom on new wood (fresh branches produced in the Spring). I have found mine to be a combination of both. If they freeze to the ground and have all dead top growth, I get far fewer blossoms than in a mild winter where they keep their old wood (this past year). I don't prune except for dead material. There is a new hydrangea out called 'Pinky Winky' that is an exception to the pruning rule. I am replacing some of mine with it. Link for picture is http://www.provenwinners.com/plants/hydrangea/pinky-winky-hardy-hydrangea-hydrangea-paniculata