Walk into any grocery store, and walk past a wall of greens, misted by water once every few hours. You’ll see the plump heads of cabbage or cauliflower — or you’ll see bundles of broccoli or stalks of kale or brussels sprouts. If you’re lucky, by the trusty turnips, will be kohlrabi (German turnips).
All these foods are unique from each other. From cauliflower rice to a kale salad, they are almost never interchangeable vegetables for most recipes. However, what if I told you they aren’t just similar to each other, but actually the same exact species?
Artificial selection of the Brassica oleracea plant is more than just a few years of choosiness. It has its origins in agriculture itself, with ties to some of the most famous books and writers in the ancient world.
The Humble Origins
Brassica oleracea, or wild cabbage, is a close sister of wild mustard. With mustard spice present at Stone Age sites 6,000 years ago, the plant genus has a long history. Pliny the Elder wrote an entire chapter dedicated to it 2,000 years ago, not long after Hippocrates used it in a medicinal paste. Mustard plants were also mentioned in 3 gospel books in the bible. (For perspective, Jesus’ birth was mentioned in 2 of the 4 gospels.)
However, while most mustard plants select for seed harvest, Brassica oleracea, also known colloquially as wild cabbage, selects for just about everything else. With origins at the advent of Mediterranean agriculture, Brassica o. has been a star of the show.
Since 2000 BC, there is clear documentation of artificial selection leading to a variety of delicious outcomes.
Kale- leaves
The oldest, and most close to the original wild cabbage, has its origins in Turkey at least 4,000 years ago. It was brought to the US in the 1890s by David Fairchild. Don’t feel bad if you don’t always like the taste of kale, because even Fairchild didn’t prefer it. However, one thing he couldn’t deny, is its health benefits. It has an excessive amount of nutrients, with a cup of fresh kale having over 100% of your daily vitamin C and vitamin K. It also has high levels of vitamin A. Its phytochemicals have shown to decrease the growths of some cancer in vitro. Furthermore, consuming kale decreased gut inflammation in mice.
If you want to grow kale you’re in luck. Kale is easy to grow in many climates, its resistant to drought, and thrives in the cold. It even becomes sweeter after surviving frost. They are pest insect resistant, more than others of the Brassica o. group. If you plant a kale seed, you can start harvesting leaves 60 days after sowing.
Broccoli & Cauliflower -flower buds
There aren’t many opportunities for eating flower buds, unless you have broccoli or cauliflower on your plate.
Genetic studies have found that early forms of broccoli before cauliflower in 5th century BC in the northern Mediterranean, and brought to the US 19th century Italian immigrants. However, cauliflower is the star of the early literary world, being mentioned by Pliny the Elder as early as 77 AD.
Broccoli is more nutritious than cauliflower, which makes sense. When mom said “eat your greens,” there’s science behind that. The green in broccoli points to it containing both more calories, proteins, and vitamins.
Cauliflowers and broccoli are easy vegetables to grow, and can get to fantastic sizes. Peter Glazebrook grew the largest cauliflower in the world, weighing in at over 60 lbs. However, they are more sensitive to dehydration and weather than other forms of Brassica o.
While growing leaves, such as kale, is quick — broccoli and cauliflower take longer. It takes anywhere from 48 to 115 days from sowing to reach harvestable maturity.
Cabbage-terminal bud
The star of the show, and the namesake of the Brassica oleracea, is the cabbage. A head of cabbage is actually saying “a head of head” in its linguistic origins, because the Latin origin of cabbage (caput) means “head.”
Fermented cabbage is still a common food throughout the world from Germanic saurkraut to Korean kimchi, with the latter having origins from over 2000 years ago. Preserving vegetables was vital to sharing foods across the world, in place of refrigeration. Nowadays, folks in the US don’t eat as much cabbage as other places, such as Russians eating 5 times more than a person in the US.
Despite being less nutritionally concentrated as kale or broccoli, cabbage still has a good source of vitamins and antioxidative phytochemicals. Growing cabbage isn’t that different from growing kale, since it doesn’t require focusing on growing flower buds like the more labor-intensive broccoli. However, instead of selecting for just leaf, cabbage selects for the leaf “head,” or the terminal bud. The terminal bud is the “the endpoint of an embryonic shoot that is not fully developed.” The embryonic shoot then bloats up instead a massive head, or a cabbage. Cabbage, like kale, will get sweeter and hardier if exposed to frost early. It’s considered a winter crop, and resists cold and drought.
If you think cooked cabbage smells a little funky, you’re not wrong. Overcooked cabbage breaks down glucosides into smelly hydrogen sulfide, which is considered flammable and toxic in mass concentrations (which you’ll never reach from overboiling cabbage).
Brussels Sprouts — lateral buds
One of the late comers to the genetic party are brussels sprouts, likely having origins in 13th century Belgium. They are similar to cabbages in that the selection was for an embryonic bud, but this time the lateral buds are selected over the terminal buds.
These lateral buds aren’t as engorged as the terminal buds, and instead increase quantity over size. To grow, they are more sensitive to drought, cold and light. Though they are frost resistant, they thrive when it’s slightly colder (59F to 64F) and full sun. After planting, you can get brussels sprouts 90–180 days later. With such a specific ideal range, it’s no wonder that their highest European yield is in the Netherlands, with 82,000 metric tons per year, with the UK having similar yield.
This high crop output makes sense — brussels sprouts actually has more vitamins per serving than cabbage. It’s nutritional but easy to transport, and can preserve freshness by transporting it on the stalk.
Studying Brassica o. forces researchers to face challenges, such as the species inability to cross pollinate with many model plants. Ning Guo and others’ 2021 survey of Brassica o. openly says the genetics of its morphological changes are poorly understood.
However, in the same paper, their genome study sheds some light. It showed the genetic differences between cabbages and cauliflower point to differences in plants’ reaction to stress. For many plants, stress prevents flower-bearing. However, for cauliflower, it reacts by making its flower buds. Furthermore, a gene in cauliflower converts from vegetative to generative growth, prioritizing flower bud selection. Further studies are needed to understand the brussels sprouts selection for lateral buds vs cabbages selection for terminal buds.
Turnips and Kohlrabi- roots and stems
Like Kale, turnips grow quickly and easily — about 60 days from planting. This also makes sense if you think about the typical priorities of any plant: leaves and roots are the most important intakes of nutrients. The origins of turnips can genetically be traced to 2000 BC Europe, with spread as far as to Japan in 700 AD.
Turnips have considerable amounts of vitamins. For example, 100 grams has 350% of your daily vitamin K intake, and a considerable amount of vitamin C. However, its protein and other nutrients levels are lower than the rest of the Brassica o. group.
In terms of growing, like much of the Brassica o. group, colder climate is better. Warm climate converts the roots to be tough and woody opposed to soft. Think of a cross between a radish and a potato: that’s the ideal turnip.
Fun fact: Turnips were not uncommon on European coats of arms. The reasons are not entirely known, but some are possibly puns. For example, the germanic Rueppen von Pfeilberg household having a turnip coat of arms makes sense, considering turnip in german is “ruebe.”
Interestingly, despite ties to turnips in appearance and name origin, the lesser known kohlrabi is a recent addition to this lineage, cultivated in 1500s southeast Asia. The lineage selects for the stem, bloating it outwards instead of causing it to grow upwards. If you’re curious about taste, kohlrabi tastes like broccoli stem or cabbage heart, though having more of a “fresh” texture compared to them. Its nutrient profile mostly shines with its vitamin C content, with nothing else notable nutritionally.
People enjoy using kohlrabi in a variety of ways — such as making fries, “noodles,” or simply steamed.
Kohlrabi hasn’t enjoyed much popularity in the US, but if you want to change that, you can grow it yourself. It’s similar to growing turnips in terms of needs, time of year, and time to harvest.
To end the Ode to Brassica oleracea, I can look at my vegetables a little differently. Not only do I see the many variations of the same plant, I see the long efforts it took to get to my plate. Not only did Brassica oleracea have origins at the beginning of agriculture itself, people have created unique varieties from BC times to the 1500s. To think deeper about your food, consider growing some of it. Maybe in time, a new Brassica oleracea can come about someday. What would you select for?
