Broccoli, cabbage, kale share an ancestor
Once in a generation or two, a leader comes forward who, defying established wisdom, is willing to speak to the fears and misgivings of the average American.
In my lifetime, that stalwart champion of the least common denominator was George H.W. Bush, who in 1990 voiced the now immortal words, “I do not like broccoli, and I haven’t liked it since I was a little kid and my mother made me eat it. And I’m president of the United States and I’m not going to eat any more broccoli.”
He probably argued with his mom over cabbage, Brussels sprouts and cauliflower, too. And if the grocers’ shelves in Greenwich, Connecticut, of 1930 had offered kale, kohlrabi and collard greens, there likely would have been battles over them as well. For all these staples of the modern healthy diet, though differing markedly in appearance, are just human-created cultivars (varieties) of the same plant, Brassica olearacea, the wild cabbage.
Wild cabbage, the grandmother of all these good-for-you veggies, is a weedy herb still found growing on stony, low-nutrient soils in coastal Mediterranean areas, and it doesn’t look much like the cabbages at Kroger or Meijer. It’s a biennial plant that stores energy during its first year of growth in a rosette of thick leaves that it uses in its second year to erect a spike of yellow flowers.
The ancients must have seen potential in the hard scrabble plant. Early forms of kale and collard greens derived from it were mentioned in “Historia Plantarum” by Aristotle’s student, Theophrastus, published around 300 B.C.
In fact, ethnobotanists suggest kale and collard greens likely were the first domesticated varieties to be developed from wild cabbages, beginning several thousand years ago with the collection of seeds from plants possessing the largest leaves. All other varieties are thought to have been derived from these forms.
The creation of head cabbages appears to have followed soon after kale, with generations of breeders selecting plants with shortened stems and ever larger leaves. By the 12th century, Mediterranean gardens contained squat plants we would recognize as cabbages, though probably without the tightly compacted heads.
Brussels sprouts may not have originated in Belgium but were being widely grown there by the 13th century. Instead of selecting for plants with big leaves, they were created as breeders focused on axillary buds along the sides of the main stem.
An axillary bud is a tiny ball of embryonic tissue found at the base of every leaf stem. It has the potential to develop into either vegetative or reproductive structures, depending on the plant’s needs. By selecting for stout-stemmed plants having enlarged axillary buds with partially opened leaves, the curiously structured “sprout stick” eventually developed–a green staff bedecked all round with mini-cabbages.
While a stalk of Brussels sprouts may appear a bit odd to some, kohlrabi could be George Lucas’s concept of what the Ewoks might have grown on the forest moon of Endor. It sits on the ground like a green softball with a handful of ungainly leaf stalks poking upward at unexpected angles.
To make one, imagine spending a hundred years or so selecting seeds from kale-like plants with abnormally thick stems just above the ground. They’ve been grown in Europe since the 15th century.
The earliest record of plants that might have been broccoli — or at least broccoli-ish — date to the Pliny the Elder’s “Naturalis Historia,” published in Rome around 73 AD. By the 16th century it was a regular component of many Italians’ diet, although it remained largely unknown in England into the 19th century and wasn’t grown commercially in the U.S. until 1920.
The plant’s name is derived from the Italian word broccolo, “the flowering crest of a cabbage,” which isn’t a bad précis of its most distinctive trait. Broccoli and cauliflower (of which was derived from one the many varieties of Italian broccoli) were developed by selecting for a profusion of immature flower heads.
Broccoli, selectively created to produce masses of green flower buds, is harvested before the flowers are allowed to open. However, cauliflower blossoms aren’t allowed to get even that far. Its surface of compact tiny bumps (“curd”) consists of thousands of malformed flower buds. Thick basal leaves surrounding the head block sunlight from reaching the curd; without being able to photosynthesize, it blanches white.
Finally, let’s not be too hard on Bush the Elder (as of Nov 25, the longest living president in U.S. history). Researchers have discovered that people who possess the TAS2R38 gene find the isothiocyanates in all these cruciferous plants quite bitter. If that’s not your experience, you’re probably among the 50 percent of Americans who have the mutant form of the gene.
But it’s a fair bet that George the First is a taster.
Ken Baker is a scientist and a retired biology professor. If you have a natural history topic you’d like the author to consider for an upcoming column, email your idea to firstname.lastname@example.org.