Celery seed comes from the wild celery plant, a stronger flavored vegetable than your run of the mill celery. The flavor of these seeds is celery-like, aromatic and astringent, but earthy and pungent. It pairs well with tomatoes, which is why you'll often see it in a bloody Mary, ketchup, and barbecue sauces. If you're short on celery, use celery seed in dishes like soups, potato and egg salad, and even pickle brine.