I generally wait till spring to prune my Annabelles and then I prune them to the ground. I like having the dried flower heads for winter interest. If you didn't prune them back before growth started this spring, that may be part of the reason for small flower heads, lack of water would certainly be another. The hydra in hydrangea lets you know they like their water.

I know I'm answering an old question - but I'm new, and couldn't resist. I have a HUGE Annabelle that covers a roughly 12X5 area, and I've experimented with pruning quite a bit. I've found that if I prune in the Fall the plant doesn't get very tall or have many flowers, and if I wait too late (past mid-March) it comes up uneven. If I don't prune at all (blame bed rest for that one!), it comes up very lanky and tall with many much smaller flowers that are a bit buried in the leaves. The perfect time seems to be late February - when there's no risk of new growth coming after a few warm days and I got to have it around most of the winter for winter interest and cover for the birds. Plus - by then I've got terrible cabin fever and am itching for my garden to come back to life!

Well... that leaves me wondering. Last year as part of fall clean up, I pruned my hydrangeas back to the central trunks (about 1-3 feet of 2-3 inch diameter). This summer I have very few blossoms, though the ones I have are large and normal-looking. They got plenty of water, as I water regularly. I assumed the lack of flowers was due to pruning. The previous six years I've lived here, I never pruned at all, except maybe a bit in the late spring to remove limbs that didn't have returning growth in them. When I didn't prune, they flowered madly.

So I assumed that pruning last fall caused the dearth of flowers. Maybe I just pruned them at the wrong time?

Well, I have really stopped pruning my Anna Bell, except for those dead stalks in the center that never green up in the spring. I have taken to reducing it's size by removing pieces of it all around the perimeter. As I transplant it all over the dry sandy loam yard (which does not get watered)- I find that those chunks in the deepest shade do not get as tall or flower as much as those that get even the shortest blast of sun. They still have a healthy growth of green- and look better than buckthorn and creeping charlie and do get a little larger every year- although much more slowly than those that get even the shortest blast of sun.
I think a blast of sun is more important to bloom than water seems to be. I also do not amend the soil where I have been planting them- I wonder if too much nitrogen might be playing a part in excessive lanky green growth.... Although Linda, with new growth dieing, I wonder if there isn't some root damage going on.... Could there be a critter up there that would want to make a home where you have planted it? Or maybe like the taste of the roots?
Come on over and we will get you a new chunk to try-

Julie

Julie, I do believe there may be chipmunks trying to take up housekeeping near the hydrangea. She is in a raised bed next to the SE side of the house, and I know they hide from the dog back there...

Have been live trapping them and taking them to a secluded area, hope to get 'em all before winter. They are SO destructive!

I am going to try cutting it back in spring and see what happens. I still have the one you gave me a couple of years ago. That one is in deep shade and hasn't blooomed yet. This one gets at least an hour of sun each day.

Linda