Broccoli, cauliflower and cabbage are three of the world's favorite vegetables, found in most temperate climates and in almost every cuisine. Despite their differences in appearance and flavor, the three are close relatives. They share many similarities with each other and their many cousins in the vegetable world, which together form one of the world's most important families of food crops.
The Brassica Family
All three of these vegetables belong to the brassicas, a genus that forms part of the larger family of mustards. They are sometimes called "cruciferous" vegetables because their four-petaled blossoms suggested a cross. These vegetables are among the world's most important groups of food crops, and brassicas are cultivated for every part of their anatomy: turnips and rutabagas for the roots; cabbages and kale for the leaves; broccoli rabe for the delicate stems and flower buds; and broccoli and cauliflower for their immature blossoms.
Cabbage and Its Relatives
Cabbage is a leafy green that forms tightly packed heads, allowing a great weight of food to be cultivated in small space. That efficiency, combined with a long harvest season, good shelf life and ease of pickling, has made cabbages a worldwide staple. The European style of cabbage heads form a firm, round cannonball shape, while Asian cabbages tend to form tight bunches that open at the top, much like romaine lettuce. Asian cabbages form a visible link between cabbages and loosely leafed brassicas such as kale and chard.
Broccoli and Cauliflower
Broccoli and cauliflower are close relatives of the cabbage, grown for their tight clusters of flower buds. The stems of cauliflower resemble the ribs of a heading cabbage in flavor, while peeled broccoli stems are difficult to distinguish from a cabbage's sweet core. A related plant that illustrates the connection is kohlrabi, which has not only vestigial leaves but a plump and crisp stem that resembles broccoli stems and cabbage in flavor. All of these vegetables are unusually nutritious, but contain complex sulfur compounds that may cause distasteful smells if they are cooked incorrectly.
Brassicas and mustards of various kinds grow wild throughout the Mediterranean, the Middle East and temperate portions of Asia. Evidence of turnip cultivation goes back 4,000 years, and many brassicas have been grown since prehistoric times. Modern cultivars derive from centuries of selective breeding and serendipitous mutations, and it is theorized that modern cultivars may all derive from as few as three original strains. A recent example of hybridization is the rutabaga, a turnip/cabbage cross dating from 17th century Scandinavia.