(Brassica napus) Cabbage relative grown for its roots, which are similar to turnips but larger, sweeter and milder. Requires a longer season, 90-120 days, but can tolerate cool temperatures as it matures, and is at its best harvested in late autumn. Sow about 90 days prior to expected fall frost, in rich, deeply worked soil of average fertility. Thin to about 8-12 inches apart, control weeds and keep moist. The leaves of some varieties make passable greens when harvested young.