Kohlrabi's exotically shaped corms are delicious streamed, boiled or eaten raw (when young.
Kohlrabi is a strange looking vegetable closely related to, but very distinct from, cabbage, broccoli, cauliflower, rutabaga, collards, and kale. Kohlrabi is grown for the enlarged bulb-like swelling (corm) that develops on the stem a few inches above the ground. From the corm sprout long petioles (leaf stems) with leaves that resemble those of the cabbage. The whole plant is less than 2 ft (0.6 m) tall. In its second growing season, kohlrabi produces a flowering stalk with numerous yellow, cross-shaped flowers that give rise to sickle shaped pods full of little black seeds. Peeled and eaten raw, kohlrabi tastes like a combination of mild turnip and sweet apple. Some liken it to the heart of cabbage or a very sweet turnip with celery or nutty overtones.
There are purple and pale green cultivars. 'White Vienna' and 'Purple Vienna' are early maturing and readily available. 'Grand Duke' is a larger cultivar that was an All American Selection, and 'Express Forcer' is a very early hybrid grown extensively for the grocery market in Europe.
Wild cabbage (Brassica oleracea ssp. oleracea), the progenitor of all the Brassica oleracea varieties, grows along the coasts in Europe and north Africa. Kohlrabi was developed from its cabbage ancestor in northern Europe, and was grown by the ancient Romans and the gardeners of the emperor Charlemagne. Today kohlrabi is a popular vegetable in Europe, Asia and the northern US and Canada. It is a staple in northern European home gardens.
Kohlrabi is fast growing, producing harvest sized corms within 50-70 days, depending on the variety. Kohlrabi is more tolerant of heat and drought than most of the cabbage relatives, and it can take frosts and freezes down to at least 10F.
Light: Best production is in full sun, but kohlrabi can stand a little shade.
Moisture: Regular garden watering. Hardiness: USDA Zones 3-10. In USDA zones 3-6, kohlrabi is planted in early spring, as soon as the soil can be worked. In zones 8B-10 it is planted in late fall or winter. In zones 7 and 8A kohlrabi can be planted in early spring and again in autumn. Kohlrabi must be harvested before warm weather sets in. Propagation: Kohlrabi is grown from seed planted directly in the garden. Thin to 6" apart and use the thinnings as salad greens.
This handsomely strange vegetable is 'Purple Vienna' kohlrabi. Download a large version of this image and put what looks like a Martian vegetable on your computer backdrop.
Kohlrabi often is steamed or boiled like turnips or cabbage, but young corms are best when eaten raw. Pick when 2-3 in (5-7.6 cm) in diameter; peel, and serve with a little salt and vinegar. Smaller corms don't need to be peeled at all. The young leaves are good and can be cooked like spinach. If kohlrabi is harvested before warm weather, it is tender, sweet and succulent. If left in the garden into the warm days of summer, kohlrabi gets fibrous and pungent, like a strong radish.
Kohlrabi is one of the most underrated and underused vegetables, especially in the US and the UK. It is one of the easiest vegetables to grow. Kohlrabi looks like something from Mars, and is a favorite with children. Kohlrabi is good for you too! It is high in potassium and antioxidants so grow some, eat some and be healthy!