Answer: Some varieties of hydrangea have a naturally floppy look when in full bloom. Thes are called mophead hydrangeas. Others have been bred to hold their blooms upright. Sounds as though your hydrangea is one of those with a tendency to flop. You can selectively remove some of the flower buds before they open so the branches are not quite so heavy on the ends, but there's really nothing else you can do, short of tying the branches to a supporting structure, to keep them upright.
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