From The Food Encyclopedia by Jacques Rolland and Carol Sherman
Also celery root, knob celery. A garden plant, celeriac, Apium graveolens var. rapaceum, from the Mediterranean region, is a highly nutritious root from certain types of celery. Like cultivated celery, it is derived from the wild celery that originated in Europe and the Middle East. It is said to have been introduced to Britain from Alexandria in the early 18th century. During Greek and Roman times, it was used to purify the blood. While used in Europe for many centuries and, to some extent, in Asia and North America, celeriac is relatively unknown in South America and Australia. Celeriac has an irregular shape and can reach about 4 inches (10 cm) in diameter and weigh as much as 11⁄2 pounds (750 g), the size of a large turnip. The brownish skin is rough and thick; the flesh is crunchy and cream-colored and tastes like celery, only stronger and slightly tangy. Easier to grow than celery, it can be easily preserved, which keeps it handy during winter. Celeriac is usually eaten raw, cut in julienne strips, cubed or grated, often mixed with a mayonnaise or mustard to create céleri rémoulade.
