DEAR AMOR: Can you help me find a cure for the Bigleaf Hydrangea that just wonât bloom on top? I only get three or four small blooms on the bottom edges. Why? â Michelle DEAR MICHELLE: Years ago, I had multiple bushes of these prolific blooming bigleaf hydrangea. I made some observations on these plants myself. Their blooms were stunningly beautiful in colors and shapes. Their light green leaves superbly hold a backdrop and bring out the bright colors of enormous pink, purple, and blue bunches of flowers. There are only a few reasons why your bigleaf hydrangea has not bloomed as expected.