Learn about growing kale varieties and the optimum choice for cold weather cropping.
Black Kale Salad Recipe
How to Grow Your Own Kale
Count kale as one of the true treasures of the fall garden, with its sweetness revealed only after old Jack Frost has kissed its leaves a time or two. This ultra-cold-hardy, leafy green vegetable is a reliable deeply satisfying addition to any cool-weather garden. Some types have tender leaves perfect for salads. Some are great steamed or in stews, and some are so hardy you can harvest them even in the dead of winter almost everywhere. And, they’re beautiful, too.
Many of the folks who buy their produce in season from local farmers have learned to love this unusual, old-fashioned fall and winter vegetable — even though they may not have grown up eating it. Kale is a little-known relative of broccoli and cabbage, with a taste that appeals to both adults and children. During my years as a kale lover, I’ve run into a number of kale-eating families with young children who relish the vegetable steamed and served simply with butter or perhaps vinegar, with salt and pepper to taste. Deb Kaldahl of the Abundant Life Seed Foundation in Port Townsend, Wash., says steamed kale is one of the few cooked vegetables her children will eat.
An elite member of a highly nutritious family of foods called the "dark-green leafy vegetables," kale is kin to broccoli and collards, which are its closest relatives; spinach: Swiss chard; and beet, mustard and turnip greens. All are good sources of vitamin K, the B-vitamin folic acid, and betas carotene, which is converted to vitamin A in the liver. Dark green leafy vegetables also are exceptionally high in other carotenoids, including zeaxanthin and lutein, which are powerful antioxidants that protect us from degenerative illnesses like cancer, cardio-vascular disease and age-related macular degeneration (the leading cause of blindness among the elderly).
For years, kale also has been touted as one of the best vegetable sources of calcium — which is especially important for vegans and others who don’t consume dairy products. The newest research on calcium’s role in human nutrition sheds even more light of how important kale, collards and broccoli can be: It shows that, in order for the body to assimilate dietary calcium, magnesium also must be present in a meal. Dairy products are rich in calcium but have relatively little magnesium. Kale and its relatives have substantial amounts of both nutrients.
Growing Kale Varieties
Kale thrives in cold weather and has a venerable history of nourishing people in the cold, dark months of the year, when few other green vegetables are to be had. The most common kale, the so-called Scotch or Scotch Curled (Brassica oleracea, Acephala group), is a primitive cabbage.
The other kind of kale, the Siberian or Napus type (Brassica napus), actually is more closely related to rutabagas. With its tender leaves, it has become popular in recent years as an ingredient in many of the imaginative salad mixes being grown by home gardeners and market farmers. Thanks to the introduction of new colors and forms in the last few years, an excellent selection of both the Scotch Curled and Napus types are available commercially.
Kale is most often grown north of the Mason-Dixon Line; Scotch kale’s botanical sister, collards, fills the same dietary niche in the South. This is due, in part, to the fact that collards taste better than kale in warm Southern summers. In fact, both greens benefit from cold temperatures that turn starches to sugars in their stems and leaves; with kale, the kind of cold that seems to really transport it from mediocre to divine is several nights of 20-degree temperatures. That means it can be a great winter crop for the South, where a few frosty nights can bring out its flavor peak by midwinter.
Over the years I’ve heard many claims as to just how cold hardy kale can be. To find out which kale could best stand up to the vagaries of short fall days and cold conditions, I enlisted the help of several kale connoisseurs from across the country: gardener and photographer David Cavagnaro in Decorah, Iowa; plant breeder and seed grower Frank Morton of Wild Garden Seed in Philomath, Oregon; and Micaela Colley, farm manager at Seeds of Change in Santa Fe, New Mexico. We also had a test site for a cold showdown in Maine, where kale often can be counted on until Christmas, but an early, very cold fall laid the crop to waste before we could get any results.
To find which varieties we could rely on for flavor, productivity and cold-hardiness in our respective parts of the country, we selected eight to test — five Scotch Curled and three Napus types, all held in high regard by kale lovers. The Scotch Curled types included a couple of reliable old workhorses, "Vates Blue" (sometimes listed as "Dwarf Blue Vates") and "Winterbor," as well as two varieties relatively new to the U.S. gardening scene: the striking, bright-red ‘Redbor’ hybrid and the Italian heirloom ‘Lacinato.’ For "Lacinato" (sometimes called black kale because the leaves are such a dark green), we used an Americanized selection and its Italian counterpart, "Nero Di Toscana." From the Napus group, we tried the beautiful "White Russian," "Red Ursa" and the feisty, cold-hardy "Winter Red," which was reported to be more resistant to cold than its progenitor, ‘Russian Red.’
Results of the Kale Trials
Recognizing that kale's flavor doesn't really develop until the first fall cold snap, many experienced growers wait until July to sow the seeds in flats for late July transplanting to the field or garden. We had ours planted out by July 10, and by late September, all three plots were producing enough for the testers to start harvesting, assessing and enjoying.
By this time of year, testers could tell why the Scotch Curled types retain such a loyal following. As a cooked vegetable alone or in soups and stews, this kale offers a sweet, full-bodied flavor. Cavagnaro, an independent spirit, stood alone in his disdain for the Scotch Curled kales. "I don't like working with the 'potscrubber' kales in the kitchen," he says. "I like the broader, smoother leaves of the Russian or Napus types." (He is, however, fond of Scotch Curled kale when it's transformed into "Krispy Kale," a snack created by Kim Blanchard of Rock Spring Farm in Highlandville, Iowa. Here's how to make it: Stem one bunch fresh kale and chop into 2-inch pieces. Toss with olive oil and salt, and place on a jellyroll pan. Crisp in a 375-degree oven for about 10 minutes. We tried it here at MOTHER and it was delicious!)
In keeping with their identity as salad greens, the Napus types were faster growing and more robust than the Scotch Curled types, which grew more slowly and deliberately. For vigor and ability to produce a steady harvest, the Napus variety `White Russian' was tops, followed by another Napus, "Winter Red."
The third variety to really shine in terms of productivity, though, was the Scotch Curled type Winterbor,' which even edged out "White Russian" and "Winter Red" in the harsh mountain climate at the Seeds of Change farm. Also showing respectable yields in this category was "Lacinato," which did significantly better than its Italian look-alike, "Nero Di Toscana." "Vates" also had a good showing for yield.
In the end, cold temperatures proved the great equalizer between the two types of kale. In Oregon, for example, a sudden, unusually frigid blast of cold, dry weather sent temperatures plummeting on three consecutive nights to 24, then 20 and 15 degrees — the coldest readings all winter. "That definitely hurt the Napus types here," says Morton, who watched as the "Red Ursa" and then the "Winter Red" got pretty badly beaten up. His "White Russian" only sustained moderate damage; the "Winterbor" and especially the "Vates" held their own.
At Cavagnaro's in Iowa, two weeks of cold, mid-November nights with temperatures dipping into the teens seriously damaged his kales by Thanksgiving Day, when the morning low hit 14 degrees. "Vates" was the clear winner with the least amount of frost damage, while "Winterbor" came in a close second. A big surprise under these conditions was how well "White Russian" held up, still retaining a number of its youngest leaves in a harvestable state despite the cold.
Colley's New Mexico plots, with cold, dry winter weather at 5,000 feet in the Rockies, yielded similar results, with "Vates," "Winterbor" and "White Russian" topping the field. According to Colley, "Vates" is the most reliable variety for living straight through the winter in New Mexico. In all three locations, "Lacinato" proved significantly more cold-hardy than "Nero Di Toscana."
When it Comes to Kale, Flavor’s the Thing
When it comes to kale flavor, which should be sweet and robust, folks who know their kales are quite passionate about their favorites. Anyone who has had the good fortune of dining on high quality, cold-weather kale from market farmers probably has tasted "Winterbor," the standard for 20 years. It is so delicious, it sets the bar.
"Vates," in our taste tests, seems quite comparable to "Winterbor," but "Redbor," despite its brilliant red color and market appeal, fell sadly short.
The best bet for improving kale's popularity among those yet unacquainted with its charms appears to be "Lacinato," however. Morton, with his years of experience growing and selling kales, says of this old Italian variety now gaining popularity in the United States, "It is not the most productive, the most cold hardy or the most uniform, but 'Lacinato' is the most sought-after by customers — and by the farm crew, too."
If you want kale for cool-weather salads, try the beautiful "White Russian" (available from seed sources 1 and 7 at the end of this article) or "Winter Red" (7). If you live where it gets cold and you want to stretch your season, be sure to grow "Winterbor" F1 (3, 4, 5, 7) and "Vates"(2, 3). If you love the flavor of cooked kale, be sure to try "Lacinato" (1 and 6). If you're really adventurous, try a little of each and enjoy kale throughout the year!
Kale Seed Sources
1. Abundant Life Seed Foundation, Townsend, WA; www.abundantlifeseed.org
2. William Dam, Dundas, Ontario Canada; www.damseeds.com (Canada only)
3. Harris Seeds, Rochester, NY; www.harrisseeds.com
4. Johnny's Selected Seeds, Winslow, ME; www.johnnyseeds.com
5. Park's Seeds, Greenwood, SC; www.parkseed.com
6. Seeds of Change, Santa Fe, NM; www.seedsofchange.com
7. Territorial Seed Company, Cottage Grove, OR; www.territorialseed.com
John Navazio, Ph.D., is director of seed grower development at the Abundant Life Seed Foundation in Port Townsend, Wash., and owner of the organic seed company Seed Movement in Bellingham, Washington.