Celeriac (Apium graveolens Rapaceum Group) is also known as 'celery root,' 'turnip-rooted celery' or 'knob celery'. It is a kind of celery, grown as a root vegetable for its large and bulbous hypocotyl rather than for its stem and leaves. The swollen hypocotyl is typically used when it is about 10â€“12 cm in diameter; about the size of a large potato. Unlike other root vegetables, which store a large amount of starch, celery root is only about 5-6% starch by weight. Celeriac may be used raw or cooked. It has a tough, furrowed, outer surface which is usually sliced off before use because it is too rough to peel. Celeriac has a celery flavour, and is often used as a flavouring in soups and stews; it can also be used on its own, usually mashed, or used in casseroles, gratins and baked dishes. The hollow stalk of the upper plant is sometimes cut into drinking straw lengths, rinsed, and used in the serving of tomato-based drinks such as the Bloody Mary cocktail. The tomato juice is lightly flavoured with celery as it passes through the stalk. Celeriac is not as widely used as some other root vegetables, perhaps because it is harder to prepare and clean. There are a number of cultivars available, especially in Europe. Among them are 'Prinz', 'Diamant', 'Ibis', and 'Kojak', which all received Royal Horticultural Society Award of Garden Merit designation in the trial in 2000. Celeriac normally keeps well and should last three to four months if stored between 0Â°C (32 degrees Fahrenheit) and 5Â°C (41 degrees Fahrenheit) and not allowed to dry out.