Celeriac is also called root celery. It has a large, knobby root with thick skin that must be peeled. Inside the flesh is sweet and peppery and similar to stalk celery in flavour.
Use: Celeriac is often cut into thin strips and used raw in salads or in soups, vegetable sdishes and sauces. It's popular in Russian and French cuisines. If you can't find celeriac, use parsnip, turnip or celery stalks.