Q.Hydrangea tree flowers are not developing petals.
This tree is at least 7 years old and has always bloomed normally. This year the blooms grew to normal size but no petals are forming- they look like they’re made of plastic. Am including a picture. Is it a result of chemical use do you think? I have to spray the photinias (located behind this tree) with antifungal spray- daconil, to prevent black spot.

Certified GKH Gardening Expert
I have never seen this happen before... So these will produce two flower types. The less conspicuous fertile flower, and the larger infertile (but attracts the pollinators) flower.
Yours is only producing fertile flowers... Very strange indeed. This could be a response to daconyl, but this is unlikely unless you are using way above the recommended dosage.
This is something that is not well documented, and that I don't see much information on. When you stop using daconyl, you can observe whether conspicuous flowers return or not.