Imagine you’re at a family reunion, and you discover that your ultra-sophisticated cousin, the one who enjoys fine wines and opera, is actually closely related to your gym-obsessed, protein-shake-chugging brother. That’s essentially what’s happening when you realise that kale, broccoli, and Brussels sprouts all come from the same plant. About 2,500 years ago, Brassica oleracea was solely a wild plant that grew along the coast of Britain, France, and countries in the Mediterranean. That wild form—known as wild mustard—still exists today, looking like an unassuming weed.
Little did it know it would one day be transformed into some of the most recognisable vegetables in the world.
Meet the Wild Mustard: The Overachiever of the Plant World
The idea that broccoli, Brussels sprouts, kale, cabbage, cauliflower, and even kohlrabi (a kind of turnip) all come from the same species sounds like the setup for a botanical prank. But it’s true. Brassica oleracea, a humble wild mustard plant, has been cultivated by humans for thousands of years, selectively bred to exaggerate different features. Want bigger, tastier leaves? You get kale. Prefer tightly packed, mini cabbage heads? That’s Brussels sprouts. Fancy a veggie that looks like a tiny tree? Hello, broccoli!
This is essentially the plant kingdom’s equivalent of dog breeding. Just as we turned wolves into everything from poodles to Great Danes, we transformed wild mustard into an entire vegetable aisle’s worth of greens. But instead of breeding for fluffiness or a strong herding instinct, humans bred Brassica oleracea for tastier leaves, fatter stems, and bigger buds.
The Mustard Cultivars
These veggies may look and taste different to you, but they all share the same genetic roots.
Kale: Ancient Greeks and Romans selectively bred wild mustard for its leafy growth, eventually developing a version that resembled modern-day kale.
Cabbage: Sometime after 1600, farmers bred mustard plants that developed enlarged leaf buds, eventually producing the tightly packed heads we know as cabbage.
Broccoli: Farmers selected plants with enlarged, edible flower buds and stems to create broccoli and cauliflower. Broccoli was first cultivated by Italian farmers over 2,000 years ago. The word “broccoli” comes from the Italian word broccolo, which means “the flowering crest of a cabbage.”
Cauliflower: Structurally alike, the key difference lies in how their flower buds develop: a broccoli’s head consists of numerous small visible flower buds, while a cauliflower’s head is made up of undeveloped flower buds tightly packed together, creating a dense, curd-like structure.
Brussels Sprouts: Brussels sprouts are developed for their numerous small, cabbage-like buds. The sprouts we’re familiar with were first cultivated back in the 13th century, in what is now Belgium. It is thought that the vegetable is named after the Belgian capital, where they became a popular crop in the 16th century.
Kohlrabi: This turnip is cultivated for its swollen, bulbous stem. Kohlrabi was first cultivated in Europe around the mid-1500s.
This process of cultivating is still happening today—like in 1993, when a Japanese seed company created broccolini by crossing broccoli with kai-lan (also known as Chinese broccoli), yet another variation of the same plant species.
Despite their differences, they all share one thing in common: that unmistakable, slightly bitter bite. That’s thanks to their glucosinolates, a natural chemical that acts as a defence mechanism against pests but also happens to give them their unique flavour (and their cancer-fighting superpowers).
So… They’re All Just Fancy Mustard?
All these vegetables—broccoli, kale, Brussels sprouts, cabbage, cauliflower, and kohlrabi—belong to the same plant species, Brassica oleracea, which is part of the Brassicaceae family, also known as the mustard family. This means they share a common ancestor with the mustard plant that produces mustard seeds like:
• White/Yellow Mustard (Sinapis alba) – Produces the mildest mustard seeds, used in classic yellow mustard and pickling spices.
• Brown Mustard (Brassica juncea) – Has a spicier kick and is used in Dijon and whole-grain mustards.
• Black Mustard (Brassica nigra) – The strongest and most pungent, often used in Indian and Middle Eastern cooking.
Some wild mustard species also exist, but these three are the most commonly cultivated for food. In simple terms: mustard seeds and these veggies are botanical cousins. They all descended from wild mustard plants, but while some were cultivated for their seeds (which we grind into mustard), others were selectively bred for leaves, stems, buds, or flowers—eventually becoming the vegetables we recognise today.
Wasabi comes from a completely different plant, Wasabia japonica, which is also part of the Brassicaceae (mustard) family but isn’t directly related to the mustard plants used for seeds.
Unlike mustard, which comes from seeds, wasabi’s spicy heat comes from its rhizome (an underground stem). The compound responsible for wasabi’s pungency, allyl isothiocyanate, is the same chemical that gives mustard and horseradish their heat—hence their similar nose-burning effect.
The Takeaway: One Plant to Rule Them All
Next time you’re staring at a plate of vegetables, wondering how broccoli and Brussels sprouts ended up in the same meal, remember: they’re just different sides of the same plant. Brassica oleracea is one of the greatest success stories of human agricultural ingenuity, proving that with a bit of selective breeding, even a wild mustard plant can transform into a nutrient-packed superstar.
And really, isn’t that kind of inspiring? If a scruffy little weed can evolve into the leafy green powerhouse that fuels smoothie bowls and Sunday roasts alike, maybe we all have a little more potential than we realise. Just something to chew on—preferably with a bit of mustard.
