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All About Kale

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The number of U.S. farms growing kale jumped from under 1,000 to more than 2,500 between 2007 and 2012.
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Chou cavalier kale grows on stems up to 6 feet high.
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Italian lacinato, also known as cavalo nero or "dinosaur" kale, grows tall in a field.
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Cold-hardy kale at the end of the growing season; frost makes the greens taste sweeter.
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Russian kales often boast red leaves with purple stems.
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An abandoned plantie crub once sheltered kale seedlings in Scotland's Shetland Islands.
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North Americans are most familiar with Scottish kale and its tightly crinkled blue-green leaves.
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Round-leaved Tronchuda kale originated in Portugal.
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A single cup of boiled kale packs lots of protein, calcium, and vitamin A -- but kale tastes sweeter when it's been seared under high heat.
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Homemade kale chips are baked with olive oil, sea salt, and often other seasonings.

“I wish people would stop calling kale a fad,” says Jennifer Iserloh. “Fads are things that don’t have legs to them, but kale has a long history.”

Iserloh is the co-author and chef behind Fifty Shades of Kale, a cheeky collection of simple yet modern recipes designed to smuggle the health benefits of kale into the bellies of people she calls “veggie haters.” She smothers kale in apricot jam and olive oil, blends it into creamy pastel-green “kale-onaise,” and tucks it unnoticed into chocolate popsicles, beef chili, and cheesy pastas. “Kale has a place in everyone’s diet,” she says.

Fifty Shades of Kale was published during what The New Yorker hailed as the “Age of Kale.” Between 2012 and 2014, National Kale Day became a thing. First lady Michelle Obama taught Americans how to make kale chips, actress Gwyneth Paltrow touted kale as “one of the best things you can put into your system,” and, according to the MyFitnessPal app, on an early January day in 2014, Americans consumed the most kale per capita in all recorded history. Quickly, kale went from unfamiliar and unappetizing to becoming the subject of memes and a popular pun for T-shirt designers.

Even vegetable growers, researchers, and breeders were unprepared for the rise in demand. “The kale movement caught a lot of people by surprise, so nobody was really working on [developing kale cultivars],” says Phillip Griffiths, a vegetable breeder at the Cornell University Agricultural Experiment Station. “Even the people who are the suppliers of kale seeds didn’t see it coming.” Between 2007 and 2012, the number of U.S. farms growing kale jumped from under 1,000 to more than 2,500. Farmers harvested more than 2,200 additional acres of kale during this period — and about 1,600 of those acres were in California alone. So many farmers scrambled onto the kale wagon that seed supplies actually ran out.

The media predicted kale would share the same fate as eating half a grapefruit for breakfast. But Iserloh is right: Kale’s been around a lot longer than the online dieting community remembers. In fact, according to the U.S. Department of Agriculture, farmers produced only marginally more kale in 2007 than in 1889. In 1909, Americans consumed 10 percent of their calcium in the form of dark leafy greens. No one was using MyFitnessPal back then, but it’s likely 2014 wasn’t actually the all-time record of kale consumption.

Most researchers believe kale is the earliest domesticated form of Brassica oleracea, the species that has also been transformed into broccoli, kohlrabi, cabbage, and Brussels sprouts by humans selecting for larger flower size, or fatter stems, or leaves that clump together to form heads. Kale looks the most similar to the wild cabbage ancestor, and was eaten in ancient Greece. By A.D. 100, the Romans had recorded 12 distinct kale-like plants.

“Ultimately, ‘kale’ is a bit of an ambiguous term,” says Griffiths, noting the many kinds of kale in the world. There are the Italian lacinatos (also known as “dinosaur”), dark green and bumpy with long, blade-like leaves. Tronchuda kales, from Portugal, bear rounded leaves with delicate white veins. Russian kales are often red with silvery purple stems, while German kale leaves are so small and smooth they look almost like spinach. Chou cavalier is a French kale that grows on stems up to 6 feet high, like a mini temperate palm tree.

But the kale type most familiar to Americans is Scottish. These kales are the familiar, stiff, tightly crinkled blue-green leaves that, 300 years before we stamped “Eat More Kale” on our clothes, comprised such a vital part of the Scottish diet that an invitation to “take your kail w’ me” meant “come over and have dinner.” Being “off your kail” meant you were ill.

Traditionally, the Scots planted kale each August in stone-walled beds known as “plantie crubs” to protect the seedlings from fierce gales. In fall, they moved the plants to the “kailyard,” a kitchen garden where these cold-hardy greens could be harvested from November to June.

 “As oats and barley were the staple grains,” Florence McNeill explained in her 1929 recipe book, The Scots Kitchen, “so kail was long the staple vegetable. His kail-yard was, in fact, to the old Scots crofter what his potato plot was to the Irish peasant.”

Visitors to 17th- and 18th-century Scotland reported that, although the food was terrible, the Scots had a health and vitality lacking in industrial-age England. John Chamberlayne wrote in 1708, “Milk-meats and oatmeal, several ways prepared, and kale and roots dressed in several manners, is the constant diet of the poor people (for roast-meat is seldom to be had but on gaudy-days); and with this kind of food they enjoy a better state of health than their southern neighbours, who fare higher.”

Perhaps it was the kale. A single cup serving of boiled kale has only 36 calories, but lots of protein, calcium, and iron, and a wallop of vitamin A. Iserloh’s goal to sneak a little kale into our daily fare might be pretty effective toward staving off deficiencies. “You don’t have to eat it every day,” she says. “Three times a week is plenty.”

But, like most of us, early visitors weren’t persuaded by glowing vitality to adopt the Scots’ kale-eating ways. “It must be freely owned that the Scots have shown very little ingenuity in the preparation of vegetables,” McNeill warns at the start of the recipe section of her book. She lists kale boiled with oats and cream, kale boiled with barley, plain boiled kale with butter, and kale boiled with a hock of ham, all cooked over a peat-burning hearth in a three-legged cauldron called, logically, the kailpot. “I always tell people not to boil it!” Iserloh exclaims. “If you do that, you cause the sulfur compounds to become more active.” This, she says, releases the stinky cabbage smell many people find disagreeable. “You need to sear it like a piece of meat. Kale sweetens under high heat because the heat caramelizes the sugar inside the leaves.”

Americans apparently have been cooking kale wrong for the last three centuries. The earliest explorers brought kale to North America in the late 1500s. The leafy vegetable became common in the kitchen gardens of colonists from England, Scotland, and Ireland, who, just like at home, boiled it throughout the winter months in hearty stews with white beans, potatoes, or ham bones.

Kale moved from kitchen gardens to the first commercial-scale farms in the 1860s. These were called “trucking farms,” and fed cities such as Philadelphia, Baltimore, and New York. Kale, available in the winter and tough enough to survive the long journey, was listed by 1889 as a “leading vegetable,” even out-producing beets. Maybe it’s coincidence, but the two states most heavily settled by the Scottish — Virginia and South Carolina — became the largest kale producers. The first popular varieties? ‘Dwarf Green Curled’ Scotch, ‘Dwarf Blue Curled’ Scotch, and ‘Tall Green Curled’ Scotch. One hundred years passed, and kale production fluctuated, peaking twice: in 1949 at 5,700 acres and again in 1997 at 5,978 acres, both just shy of the 6,256 acres that caused the 2012 seed shortage. The media was unimpressed. Vegetable researchers studied other things.

And today? “We’re doing a lot of work with kale,” Griffiths says. He and graduate student Hannah Swegarden are working to develop new cultivars for modern kale eaters. The difference, he says, is that we no longer just boil kale into broth. Now it’s trendy to eat kale raw, as a salad, a smoothie, or myriad other ways.

“It’s actually a good trend in society,” says Griffiths, “because kale is much more nutritious than other leafy greens, especially more so than lettuce, so people moving to kale as a leafy green base is actually a good move.”

New recipes have given him and Swegarden ideas. Luckily, kale has plenty of genetic diversity for them to work with. “If it’s being consumed in a salad, you want something that’s less bitter and has more of a crunch to it, like a romaine lettuce,” says Griffiths, describing his new favorite, a golden kale with purple ribbing and a juicy snap. These new cultivars won’t be in supermarkets for a few more years, so Griffiths and Swegarden are betting on kale staying relevant.

But since the USDA hasn’t published a follow-up, it’s unclear whether kale production is continuing to rise, or if we Americans have gone off our kale again.


Kale in the Garden

Species:Brassica oleracea var. acephala

Description: Cool-weather vegetable with edible leaves; kale plants don’t form heads, thus, “acephala” from a Greek word meaning “headless”

Days to Maturity: 50 to 80 days

Growing Conditions: Sunny, fertile spot with lots of compost in the soil; space seedlings 14 inches apart in all directions

Turn your kale into crispy, salty kale chips with our Kale Chips Recipe.


Lindsay Gasik is a fruit-hunting geek and horticultural tour guide in Malaysia and Thailand. Follow her at Year of the Durian.

Published on Nov 27, 2017

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