We have a hydrangea tree. I pruned it last fall. Now it has tons of large flowers on it. After a hard rain, all the branches bent over, almost hitting the ground. What can I do to make the branches stronger? They are large and thick but not strong. I had to cut all the flowers off to save the tree.
Weather can be harsh on the Hydrangeas when the wind and rain combine with very heavy flower heads.
Little can be done now but make sure the plant is growing in good conditions to insure healthy stems.
Over fertilizing can cause weakened stems.
Also next spring you can use a round plant support.
Here is a link with more information.