a well-known plant of the mustard family, cultivated for its edible roots, but unknown in a wild state. It is a native of Asia, but now flourishes in all temperate regions. It grows to about three feet in height and bears nearly white flowers, on a branched stalk. Some species are annual, and some are perennial. The roots of some varieties are globular in form, those of other species the roots are white, while in others they are red. The seeds are sown in rows about a half-inch apart, and they mature in from three to five weeks. Often three or more crops may be raised in a season.