Celery seeds are not from the familiar crunchy vegetable, but from so-called wild celery (apium graveolen), which is inedible (possibly poisonous) and foul smelling. But the seeds are very nice - with a strongly grassy/celery aroma and warm, bitter bite. Use whole with almost everything, but famously good with tomatoes (Bloody Marys, Caesars), coleslaw, fish, eggs, salad dressings, vegetable soups and savoury baked goods.