I only remember a couple pages from this book from my childhood, but the images haunt me-would love to see the book today: The book has colorful illustrations of a horse walking down a street lined with fruit/ flower stands. The horse has on a wide- brimmed hat, I believe made of flowers.
Is this possibly Robert the Rose Horse, by Joan Heilbroner, illustrated by P.D. Eastman? If you Google that title you should come across somebody reading the book on YouTube or something, and you can see whether it’s the book. I’m not sure this is it because, although the book features roses (and an allergy thereto), I don’t think it quite fits the description. But maybe. Good luck!