Broccoli, cauliflower, cabbage, kale, Brussels sprouts, and kohlrabi all come from the same wild mustard plant. They’re not just relatives. They are literally the same species, shaped over centuries of selective breeding into vegetables that look nothing alike. Think of it like dog breeds: a Great Dane and a Chihuahua are both dogs, and broccoli and cabbage are both wild mustard.
The ancestor behind all of them is a scrubby, weedy plant called Brassica oleracea, which still grows wild along the coasts of Europe. Farmers didn’t crossbreed it with other species to get these vegetables. They simply selected for different parts of the same plant, generation after generation, until each one became its own distinct crop.
The Six Major Vegetables
Each of the six main cultivars exists because farmers in different times and places noticed variation in a specific part of the wild mustard plant and kept breeding for more of it. The part they focused on is what makes each vegetable recognizable today.
Kale is the closest to the original wild plant. Farmers selected for large, robust leaves without any head formation. The plant stays open and leafy, which is why kale looks more like a weed than something engineered. Collard greens followed a similar path and are sometimes grouped in the same category.
Cabbage came from selecting plants whose leaves folded tightly around a central growing point, called the terminal bud. Over time, this produced the dense, compact head you see at the grocery store. Within cabbage alone, there are multiple forms: green cabbage, red cabbage, savoy cabbage with its crinkled leaves, and others.
Brussels sprouts are essentially tiny cabbages, but they form along the main stem rather than at the top. Farmers selected for plants that developed many small, tight buds at the base of each leaf along a tall stalk. The main stem grows 2 to 3 feet tall, with sprouts only 1 to 1.6 inches in diameter lining it from bottom to top.
Broccoli was bred for its flower buds. Wild mustard produces small clusters of yellow flowers, and farmers selected plants with much larger, tighter bud clusters on thick stems that held in that immature stage longer before blooming. When you eat broccoli, you’re eating a mass of unopened flowers.
Cauliflower looks similar to broccoli but is botanically different in a surprising way. The white “curds” of cauliflower are not flower buds at all. They’re a structure that keeps replicating itself in a pattern without ever actually producing flowers. It’s a developmental quirk that farmers selected for, producing a vegetable that stays in a permanently pre-flowering state.
Kohlrabi is the oddest looking of the group. Farmers selected for a swollen, bulb-like stem that forms just above the soil line, typically 2 to 4 inches in diameter. It originated in Europe during the Middle Ages. The rate of that stem swelling is largely genetic, taking anywhere from 4 to 12 weeks depending on the variety.
Beyond the Big Six
Those six get the most attention, but at least 12 additional crop types have been developed from the same wild mustard species. Some are well known in certain cuisines but unfamiliar in others.
Chinese broccoli (gai lan) is a leafy vegetable with small florets, popular across East and Southeast Asian cooking. It was even crossed with conventional broccoli to produce broccolini, the slender-stalked hybrid now common in Western supermarkets. Romanesco, with its striking fractal-patterned head, is technically a variant of the same group as cauliflower. Walking stick kale grows 6 to 12 feet tall and was historically dried and used as a literal walking stick. Other lesser-known forms include tronchuda kale (a Portuguese variety), perpetual kale, and marrow cabbage.
How One Plant Became So Many
The key to understanding this is that every plant has leaves, stems, buds, and flowers. Wild mustard has all of these in modest proportions. What humans did was exaggerate one part at a time. Select for bigger leaves and you get kale. Select for a tighter terminal bud and you get cabbage. Select for more flower tissue and you get broccoli or cauliflower. Select for a fatter stem and you get kohlrabi. Each lineage was pulled in a different morphological direction, but the underlying DNA is still the same species.
This is why all these vegetables share a similar peppery, slightly bitter flavor profile. They all produce the same family of sulfur-containing compounds called glucosinolates, which are responsible for the sharp taste of raw cabbage, the bite of broccoli, and the smell that fills your kitchen when you cook any of them too long. Broccoli alone contains at least 12 different types of these compounds across its seeds, sprouts, and florets. These are the same chemicals that give actual mustard its kick, reinforcing just how closely related all these plants remain despite looking so different on the plate.
Mustard the Condiment vs. Mustard the Family
There’s one point of confusion worth clearing up. The yellow mustard you put on a hot dog comes from the seeds of different but related plants in the same botanical family. Brown mustard, yellow mustard, and black mustard are separate Brassica species (or close relatives) bred specifically for their spicy seeds. Wild mustard, the ancestor of all the vegetables above, is a different species within that same family. They’re cousins, not the same plant.
So when people say broccoli “comes from mustard,” they mean it descends from a wild plant in the mustard family, not that it was somehow derived from the condiment. The entire family, sometimes called the cruciferous or cabbage family, shares common traits: four-petaled flowers arranged in a cross shape, pungent sulfur compounds, and similar seed pod structures. Turnips, radishes, arugula, horseradish, and watercress all belong to this broader family as well, though they come from different species than the Brassica oleracea group.
Why It Matters at the Grocery Store
Knowing these vegetables are the same species explains a few practical things. They’re all susceptible to the same pests, which is why gardeners rotate them as a group and avoid planting broccoli where cabbage just grew. They cross-pollinate easily, so saving seeds from a kale plant growing near a Brussels sprout plant can produce unpredictable offspring. And nutritionally, they share a common baseline of vitamins, fiber, and those glucosinolate compounds that have been widely studied for their potential health benefits. The differences in nutrition between, say, broccoli and cauliflower come down to which specific compounds accumulated more in one cultivar than another, not from any fundamental difference in their biology.
Next time you look at a produce aisle and see kale, cabbage, broccoli, cauliflower, kohlrabi, and Brussels sprouts lined up as though they’re entirely different foods, remember: they’re all the same plant wearing different outfits, shaped by centuries of farmers who each had a different idea of which part was worth eating.