Kohlrabi

Round, swollen stems with crisp, sweet flavor. Performs well in cool-season planting. Leaves are edible as well. Excellent raw in salads or roasted, sautéed, or in slaws. 
Status: Heirloom brassica
Days to maturity: 50–60
Harvest size: 3–4 inches diameter
Cold hardiness: Hardy in zones 5–9