I wrote about factors limiting hydrangea bloom to member Kenn some months back when he asked about feeding them, as I recall (read his original question and the first reply or so): http://awaytogarden.com/forum/viewtopic.php?f=25&t=40&hilit=hydrangea%2A Basically plants don’t flower because they are not getting enough light, are getting too much Nitrogen (so they grow lots of green but no blooms) or were pruned at the wrong time. I go into this in more detail in the answer above. Very hard late frosts can also be a culprit. I am assuming you have mophead-type blue H. macrophylla, which are normally pruned right after bloom if needed by removing the oldest flower stems to the ground to let in more light and allow younger stems to develop. When you say you have been deadheading, was there any trimming in fall or spring?