Recently kale has become the vegetable poster child for eating healthy. Without a doubt, it deserves approbation for being a great source of vitamins, minerals and fiber, and for containing anti-inflammatory and anticancer properties. Its beauty, ease of cultivation, hardiness and good taste make it an essential vegetable for the kitchen garden and the table.
I don’t remember why I decided to plant my first crop of kale. I direct-sowed the seed in late spring, and most of the seedlings outgrew the assault of flea beetles. After thinning, I left the plants to expand their bouquets of blue-green frilly edged leaves. By late summer, I decided to try a few of the older leaves at the bottom of the stem and steamed them. They were pretty tough and leathery. I wasn’t too sure about the merits of this plant. Fortunately, I persisted, steamed up some delicate younger leaves, and today kale graces my garden every year. If I could grow only one vegetable, kale would be that singular plant.
Kale belongs to the family Brassicaceae and is characterized by its four-petal flowers, often yellow or white, arranged in the shape of a cross. This family includes such edibles as arugula, broccoli, cabbage, horseradish, mustard, radish, rutabaga and turnip.
It is a member of the species known by its Latin binomial as Brassica oleracea, which includes five or six different forms or groups. Those groups are further divided into subgroups, all of which are collectively known as cole crops.
In the Beginning
Wild Brassica oleracea is a short-lived perennial originating on rocky limestone cliffs in coastal northwestern Spain, western France, and southern and southwest Britain. A number of closely related species capable of interbreeding occur in southern Europe and northern Africa.
Cultivated kale is a biennial, flowering in its second year after a cold period. Plants may persist for a number of years, especially if their flowers are repeatedly removed in the spring.
Kale may have arrived on North American shores by 1631, purchased as colewort seed by John Winthrop Jr., the governor of Colonial Connecticut, from grocer Robert Hill. It was cultivated throughout colonial times and continuously through the 19th and 20th centuries. Fearing Burr in his The Field and Garden Vegetables of America mentions more than a dozen varieties of Borecole. William Tracy’s List of American Varieties of Vegetables published in 1903 enumerates 100 types of kale carried by American seed companies.
In the Soil
Kale is one of the easiest vegetable plants to grow. It does best in rich, well-drained soil, neutral to somewhat alkaline, with good moisture throughout the growing season, although it is not fussy. Under good nutrient conditions, plants can become quite large and robust. I like sowing seeds indoors and setting out transplants in early spring so I can get fresh kale leaves by June. Seeds can be direct sown for late summer to fall harvest. Plants are frost hardy, and some types can survive well below 20 degrees Fahrenheit with stems or roots surviving subzero temperatures. Most types of kale will take frost down to at least 26 degrees without any damage.
Enjoy a long season with kale, beginning in spring, by eating smaller developing leaves and bud stalks from the overwintered plants, using young leaves in salads or braised, and harvesting mature leaves through December or January. Frozen leaves on the plant can be defrosted and often taste fairly good. In warmer climates, the plants can be harvested throughout the winter. In order to ensure a winter harvest or to overwinter plants, grow the plants in a greenhouse, under some form of high tunnel, or protected by a few layers of agricultural fabric.
While relatively tough, kale is subject to a number of insect enemies such as flea beetles when young, cabbage worms, slugs and, of course, four-legged critters, especially woodchucks and deer. It is also subject to a number of diseases, although generally this is not problematic in small stands with good soil and proper rotation.
My overall favorite kale is Dwarf Blue Curled Scotch, which is usually just called Blue Curled Scotch. This kale grows from 14 to 20 inches tall. It is a vigorous plant with curly edged, blue-green, up-to-1-foot-long leaves with a lighter green stalk. The plant is tough and will overwinter in many locations, especially with snow cover. Like many kales, the leaves improve after a frost, becoming both sweeter and more tender. Widely circulated in the mid-19th century, this kale, or similar forms, is considerably older. In 1936, the Virginia Truck Experiment Station released a strain of this kale and named it V.T.E.S., the acronym for the experiment station, which became known as Dwarf Blue Curled Vates, an improved version of Dwarf Blue Curled Scotch, as it is more cold-hardy and uniform.
A wide range of curly varieties of varying sizes have been cultivated and, according to C.L. Allen in 1901, “the nomenclature of this vegetable is decidedly mixed.” For example, Green Curled Kale was another of the Scotch kale group and an old type, somewhat taller in stature, and another was called Dwarf Green Curled Scotch.
Siberian kales with flatter leaves are usually Brassica napus, a different species, yet the curly types seem to be Brassica oleracea. The Siberian varieties have a bit more of a tender leaf texture, and at least one variety is available today.
Be aware that, as in 1901, many varieties of kale, Siberian and otherwise, are currently on the market, along with many new open-pollinated varieties and hybrids representing both species and some in between.
Ragged Jack is another hardy kale dating to the late 19th century and originating in Russia. Also known as Russian Red kale, its blue-green leaves have a hint of red, which can become more pronounced in certain locations and with cold weather. The leaves are relatively flat, oaklike in appearance, with irregular deep lobes, and they sometimes become frilly with a prominent reddish midrib with red veining.
Just to confuse matters, this kale is considered a Brassica napus ssp. pabularis, not B. olearacea. The napus brassicas are derived from B. olearacea and are more closely related to rutabagas. The leaves are soft-textured, and the stems can be somewhat delicate and subject to wind breakage. The plant stands 2 to 3 feet tall.
Cavolo Nero di Toscana kale has a variety of names, including Lacinato, Dinosaur and Black Tuscan. This kale is different from its fellows. A gorgeous plant with dense-growing, upright and heavily puckered, or savoyed, narrow leaves, it is deep bluish-black-green with a pale midrib. Leaves are a couple of inches wide and can be more than a foot long. It is a traditional Italian variety, which probably dates to the 16th century. Although it is frost-hardy, as the weather dips into the low 20s, the leaves start to burn and it will only overwinter in mild climates.
A number of different smooth and non-frilly heirloom collards are available, along with the Portuguese kale, Couve Tronchuda. So whatever species you are eating – whether heirloom or modern, hybrid or open-pollinated – if it is called kale, it is going to be really good and nutritious.
I have one culinary hint: Don’t overcook the leaves. A slow sauté or steaming works just fine.
Lawrence Davis-Hollander, former director and founder of the Eastern Native Seed Conservancy, is now a principal of Dandelion Gardening Arts in Connecticut.