(Brassica oleracea) Kohlrabi is a cabbage relative with a difference: the main crop is the stem, which has been selected over the centuries to grow as an oblate sphere, about the size of an apple. Well grown, this stem is juicy and crisp, and tastes similar to a cabbage heart. The leaves are edible too, especially when young. Plants thrive in cool weather and develop an especially sweet flavor when exposed to a light frost. This crop tolerates heat better than most cabbage relatives, and can be grown straight through the summer in most areas of the country. Sow seeds ¼ inch to ½ inch deep. Ideal germination temperature is 70-75 F. Seeds germinate in 8-10 days. When seedlings are about 4 inches tall, thin to 5 inches apart. Harvest bulbs when they are more than 2 inches in diameter. Kohlrabi is a good candidate for succession sowing. Sow again in late summer for a fall harvest.