[Su Hao (Viet); Ganth Gobhi (Hindi); Knol-Khol (Tamil); Monj-hakh, Haakh (Punjab); B. oleracea group Gongylodes]
Like head cabbage, broccoli, cauliflower, kale, collard greens, and Brussels sprouts, Kohlrabi was created from wild cabbage by human selection. It may look like it belongs with the root cabbages but the "bulb" is actually a swollen stem so it's all "greens", and is similar to broccoli stem, but sweeter and easier to work with.
Generally, Kohlrabi are eaten fairly small because they become woody as they grow larger, but one cultivar, Gigante, is still edible in larger sizes. Kohlrabi are usually marketed at about 2 inches in the spring and 4 inches in the fall. Young kohlrabi can be eaten raw in salads as well as being cooked.
More on Cabbage Greens.
Kohlrabi aren't necessarily green, but you won't find purple ones in your local supermarket, only in the more adventurous farmer's markets. The interior of the purple stem is pale, like the green kohlrabi.
While developed in Europe, and usually associated with northern Europe, kohlrabi is well known in temperate zones from Pakistan through China. It is an important vegetable in Kashmir, where they also grow a version without a swollen stem, just leaves, called Haakh. The bulb version is called Monj-haakh. As Knol Khol and Ganth Gobhi it is popular in other parts India, mostly in the north. In some parts of China it is called "Jade Turnip".
Kolrabi leaves are quite edible and nutritious, but they are tough, much like Collard Greens, and need to be simmered at least 45 minutes to be tender. Leaf stems will still be crunchy and a bit fibrous with that length of cooking.
Buying: This vegetable is so popular in the German speaking parts of Europe, nearly every supermarket and produce market in North America has it. To avoid fibrous bulbs, In the spring, buy them at about 2 inches diameter, and about 4 inches in the autumn.
Storage: In the refrigerator, the leaves will yellow in a few days, but the stem can be stored for up to a month loosely wrapped in plastic. If you bought leafy ones, just cut them off, leaving a inch on the bulbs. Cook them as greens.
Prep: Slice about a quarter of an inch off the root end, then peel. There are two layers of fiber under the skin but they are thin and easily seen. Slice, dice or julienne as needed by the recipe.
Cooking: Young Kohlrabi is often used raw in salads and slaws, and I have found bulbs up to 4 inches to be fine for this use late in the year. The greens can be used interchangeably with Collards or Kale or Chinese Broccoli.
Health & Nutrition: Like other members of the cabbage family, Kohlrabi is highly nutritious, with plenty of vitamin C, vitamin A (especially the greens), vitamin K, and B-complex. It provides minerals copper, potassium, manganese, iron, and calcium, and is high in fiber and low in calories. It also has a good selection of phytochemicals, such as isothiocyanates, sulforaphane, and indole-3-carbinol that are thought to protect against prostate and colon cancers, along with plenty of antioxidants.cb_kohlrz 161205 - www.clovegarden.com