As 1600hp notes, getting a full-size tree out of the Staff of Flowers is probably not intended, especially as it would substantially duplicate the functionality of the rare, single-use Feather Token (Tree).
(You could argue that a typical cherry tree isn't quite the same thing as the 60 foot oak created by the Feather Token, but there are other flowering trees that can grow much larger. How about a liriodendron (tulip tree), for example?)
That said, creating a cherry blossom without a tree feels weird, too. Where would it grow, then? Just flat on the ground? So I'd be inclined to let it create a tree, if only so that the blossom won't look out of place.
That said, nothing in the description of the staff says that it has to be a full-size mature tree. So a reasonable DM could well rule that the staff creates a small cherry tree sapling, maybe a few handspans tall, with a single blossom on it.
That'd be as biologically plausible as anything the staff does (real trees can and do grow and flower like that, especially if their growth is naturally or artificially stunted; just Google "bonsai cherry tree" for some examples) and seems mechanically balanced.
And you do get a real cherry tree out of it — you'll just have to wait a few years for it to grow to full size. :)