Celeriac is a root vegetable native to southern and northern Europe where it grow wild. Celeriac is edible raw or cooked, but it is most commonly found in soups and casseroles. Leaves and foliage have an intense flavor and is usually used as a garnish in fine-dining restaurants. It can be stored for up to 8 months in a cool dry place. A sign of rotting is an overpowering flavor of celery.