The celery root is the main taproot that grows downward as celery grows upward. Celery root is also known as celeriac, turnip-rooted celery, and knob celery. Normally a distinct variety of celery is used when growing roots for food. The root is used when it is about the size of a baseball or softball. Celery root is normally peeled and cooked. It is often mashed or used in casseroles and baked dishes. The celery root is routinely used in French cooking and is seen throughout Europe. Celery root tastes somewhat like celery and parsley.
Celery roots are available year-round with a peak during November through April. Select roots that look like they would be easiest to clean and peel; the roots can have lots of knobs and crevices full of dirt. Medium roots tend to be smoother and harder and these roots can be sold with or with out the celery tops. If you do buy the roots with the tops, trim the stalks and save them for soups and stews. The roots should be wrapped in plastic, stored in the refrigerator, and used within a week. Celery roots must be scrubbed, trimmed at the top and bottom, quartered, and then peeled before eating. Be sure to discard any spongy parts. Avoid overcooking celery root as it will go quickly from firm to mushy.