The largest flower auction in the world is in Aalsmeer. There’s an interesting video clip of it here.
I found this advertisement in The Weekly Florists Review, Vol. 12, 1903:
Geo. E. Bradshaw John R. Hartman
53 West 28th Street, New York
Telephone 1239 Madison Square
Mention the Review when you write.
There have been flower wholesalers on this section of 28th Street since the 1890s, according to this interesting article in The Economist.