What variety of squash produces "flor de calabaza"?
They're commonly called squash blossoms in English - as you might guess, this is because it doesn't matter too much what kind of squash they're from. They'll most commonly be from smaller summer squash plants (e.g. zucchini) though, since they produce many small squash instead of a few large squash (like pumpkins), so you can get more blossoms for your trouble.