I have two dahlias that are lush and green. They look wonderful, except for one thing... They no longer produce ray florets. When I bought them two years ago they made beautiful orange semi-cactus blooms, but now they only make green sepals.
See the thread below. Did your blooms look anything like that? I've since read it was probably a plant infected with Aster Yellows. The plant was fully developed, looked healthy til the buds opened.
Here is a link that might be useful: Possibly aster yellows
thanks! that looks like it might be the case. This is three buds on two plants yesterday :(