Kohlrabi is a spring vegetable which is now available year-round. It is eaten both raw and cooked and its flavor resembles that of broccoli, but it has a slightly sweeter and milder taste. Kohlrabi is grown mainly in German-speaking countries and unlike other known varieties of cabbage, it develops through a thickening of the middle stem and not from the leaves or flowers.
From Wikipedia: “Kohlrabi (German turnip or turnip cabbage; Brassica oleracea Gongylodes Group) is a biennial vegetable, and is a low, stout cultivar of cabbage. Kohlrabi can be eaten raw as well as cooked. Edible preparations are made with both the stem and the leaves.”
“The name comes from the German Kohl ("cabbage") plus Rübe ~ Rabi (Swiss German variant) ("turnip"), because the swollen stem resembles the latter. Kohlrabi is a commonly eaten vegetable in German-speaking countries, but is also very popular in the northern part of Vietnam where it is called 'su hao', and in eastern parts of India (West Bengal) and Bangladesh where it is called 'Ol Kopi'. It is also found in the Kashmir valley in north India and is there known as 'Monj-hakh', 'monj' being the round part, and 'hakh' being the leafy part. This vegetable is called 'Nol Khol' in the north of India, and in Ceylon as 'Nol col' (the Turnip Cabbage).”
“Kohlrabi has been created by artificial selection for lateral meristem "growing" (a swollen, nearly spherical shape); its origin in nature is the same as that of cabbage, broccoli, cauliflower, kale, collard greens, and Brussels sprouts: they are all bred from, and are the same species as, the wild cabbage plant (Brassica oleracea).
The taste and texture of kohlrabi are similar to those of a broccoli stem or cabbage heart, but milder and sweeter, with a higher ratio of flesh to skin. The young stem in particular can be as crisp and juicy as an apple, although much less sweet.
Except for the Gigante cultivar, spring-grown kohlrabi much over 5 cm in size tend to be woody, as do full-grown kohlrabi much over perhaps 10 cm in size; the Gigante cultivar can achieve great size while remaining of good eating quality. The plant matures in 55–60 days after sowing and has good standing ability for up to 30 days after maturity. The approximate weight is 150 g.”
“The flavor of kohlrabi comes from the sugar, fruit acids, and mustard oil glycosides it contains. In the case of fruit acids, malic acid and citric acid dominate.
In comparison to the bulb, kohlrabi leaves contain about twice as much vitamin C, one hundred times as much carotene, and ten times as much calcium and iron.*”
“There are several varieties commonly available, including White Vienna, Purple Vienna, Grand Duke, Gigante (also known as "Superschmelz"), Purple Danube, and White Danube. Coloration of the purple types is superficial: the edible parts are all pale yellow. The leafy greens can also be eaten. One commonly used variety grows without a swollen stem, having just leaves and a very thin stem, and is called Haakh. Haakh and Monj are popular Kashmiri dishes made using this vegetable. In the second year, the plant will bloom and develop seeds. Kohlrabi also comes in three different colors: white, purple, and pale green.”
Preparation and use:
“Kohlrabi stems are surrounded by two distinct fibrous layers that do not soften appreciably when cooked. These layers are generally peeled away prior to cooking or serving raw, with the result that the stems often provide a smaller amount of food than one might assume from their intact appearance.
The kohlrabi root is frequently used raw in salad or slaws. It has a texture similar to that of a broccoli stem, but with a flavor that is sweeter and less vegetal.
Kohlrabi leaves are edible and can be used interchangeably with collard greens and kale.
Kohlrabi is an important part of the Kashmiri diet and one of the most commonly cooked foods. It is prepared with its leaves and served with a light soup and eaten with rice. Some varieties are grown as feed for cattle.”
Note (italics): * = Translation from a German Wikipedia entry