How Does Kale Grow?

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USDA Hardiness Zones:  6 to 11

 

Kale, a relative of cabbage, is a widely adaptable and genetically diverse plant with large, frilly leaves. It grows successfully in nearly every region of North America, from Alaska to Florida.

 

Kale prefers cold weather and is said to taste better after it has been touched by frost. In areas where the temperature drops below 20 degrees Fahrenheit, kale is planted any time between early spring (3 to 5 weeks before the last frost) and late summer (6 to 8 weeks before the first frost). Kale also thrives in warmer regions of the south and mild coastal regions that rarely experience frost, but should be planted there in winter for best results. 

 

Kale grows best in full sun, but tolerates partial shade as well. It prefers fertile, nitrogen-rich soil with neutral pH levels. To produce fast-growing plants with tender leaves, the soil is enriched with fertilizer and compost before planting seedlings. 

 

When planting kale, it is important to note that leaves grow larger if seedlings are spaced farther apart, however, plants with smaller leaves tend to be more tender and flavorful. Most kale grows into whatever space is provided (within reason).

Seasonal Growth

 

Health Benefits

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Due to its powerful combination of vitamins, iron, calcium, and antioxidants, kale has earned a multitude of nicknames such as “superfood,” “the green queen,” “the powerhouse vegetable,” and “the new beef.” Following are the health benefits of the popular super green:

 

Kale is the top producer of vitamin C in the leafy green vegetable family, and even beats out oranges with 80.4 grams per cup, providing 134% the recommended daily value in one serving. The high vitamin C content is essential for a healthy immune system, and assists in hydration and metabolic functions. 

 

Kale is also high in vitamin A, which promotes a healthy immune system, vision, and skin, and helps prevent some cancers, including cancers of the oral cavity and lungs.

 

The high vitamin K content in kale--a whopping 684% of the body’s daily requirement in one serving--is also noted for its cancer preventative properties. Studies have shown vitamin K to suppress the growth and invasion of hepatocellular carcinoma, a form of liver cancer. There have also been instances when the vitamin has induced certain varieties of human leukemia to turn into normal white blood cells, and to halt the reproductive cell cycle in some forms of brain tumors and stomach cancers. Vitamin K also promotes antioxidant activity, bone health and healthy blood clotting. 

 

Per calorie, kale contains more iron than beef. Iron is essential in the formation of hemoglobin and enzymes, the transport of oxygen through the body, cell growth, and muscle, brain and liver function.

 

Kale is an anti-inflammatory powerhouse, filled with omega-3 fatty acids that fight against autoimmune disorders, arthritis, Alzheimer’s disease, and asthma.

 

At 90 grams per serving, kale contains more calcium than milk and is absorbed by the body more easily than dairy products. Calcium plays an essential role in bone and tooth formation, as well as blood clotting, nerve impulse transmission, muscle contraction, and healthy blood pressure.

 

One cup of kale contains just 36 calories and zero grams of fat, but is high in protein (three grams) and fiber (five grams), which makes it a great digestive aid. It is also high in sulfur, which, like fiber, is a detoxifying agent for the body that helps promote a healthy liver. Kale also helps lower cholesterol levels, making it an excellent food for cardiovascular support. 

 

Kale is high in antioxidants, including flavonoids and carotenoids, that help protect against various cancers. It also contains the antioxidant alpha-lipoic acid, which has been shown to lower glucose levels, increase insulin sensitivity, and prevent oxidative stress-induced changes in people with diabetes. 

 

The high potassium content in kale is associated with reducing risk of stroke, preservation of bone density, muscle health, managing blood pressure, and the prevention and reduction of kidney stones.

History

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Brassica oleracea species (which includes, kale, broccoli, cabbage and other greens) are native to the Mediterranean region of Europe. The ancient Greeks cultivated leafy greens such as kale and collard greens more than 2,000 years ago, and documented boiling them as a cure for hangovers. Early Roman manuscripts also refer to “brassica,” and it is said that Julius Caesar consumed kale before royal banquets to prevent indigestion. 

 

European manuscripts dating as early as the first century also describe leafy green “coles,” which may have arrived in Britain and France via the Roman empire, or earlier via the Celts. By the Middle Ages, kale varieties had spread throughout Europe, to Russia and southeast Asia. In 19th century Scotland,  where the plant was a staple due to its cold-hardiness characteristics “kail” was a generic term for “dinner.”

 

The first mention of kale, or “colewart”, in North America was in 1669, although it was likely introduced by English settlers earlier than its first documentation. Kale’s popularity spiked in the United States in the first decade of the 21st century due to its excellent “superfood” nutritional qualities. Since 2008, kale has seen a 400% increase on restaurant menus across the nation.

 

Propagation

 

Kale is propagated by seed, either directly or started indoors for transplanting. Although kale seeds germinate in temperatures as low as 40 degrees Fahrenheit, the optimum temperature for germination is between 55 and 75 degrees Fahrenheit. 

 

Kale seedlings do best in nitrogen-rich soil provided by adding bone meal or composted manure. Seedlings are planted approximately ¼” to ½”  deep, one inch apart, in rows that are spaced 8 to 24 inches apart. Soil is kept moist during germination to prevent it from forming a crust that may cause uneven germination. 

 

Seedlings planted indoors are ready for transplanting once they have at least three or four leaves, and the outdoor daytime temperature has reached 50 degrees Fahrenheit. 

It’s recommended that growers stagger planting for a continuous harvest.

 

Harvesting

 

Although kale prefers cooler weather, it is an adaptable and hardy plant that can be harvested at various times throughout the year. Kale leaves are sweeter when they are picked after a  frost. 

 

Most varieties of kale are usually ready to harvest 70 to 95 days from seed, and 55 to 75 days from transplanting. Baby kale leaves, which are sweeter and more tender than mature kale leaves, can be picked anytime after 30 days after planting . 

 

Individual leaves can be cut from the plant once it reaches 8 to 10 inches in height. The outside leaves are picked first leaving the center terminal bud in place to produce more leaves.  If leaves are tough or brown, they are already too old and should be removed. The tender baby leaves are cut from the inside of the plant. 

 

To remove the entire bunch of kale at once, it is cut at the roots. 

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Storage

 

Kale is best kept in the refrigerator, preferably in a hydrator drawer, for up to one week. To store in the refrigerator, unwashed kale is placed in a plastic bag or wrapped in a damp paper towel. It should only be washed just before using. If the leaves begin to wilt plunging them in cold water for 10 minutes will re-hydrate them.

 

Kale keeps for up to 10 to 12 months in the freezer. It is first blanched for two minutes and then chilled quickly in ice water. The excess water is squeezed out and the leaves put in an airtight plastic bag.

 

Fun Facts

 

The top five commercial producers of brassicas (including kale, cabbages, brussels sprouts, kohlrabi and collard greens) are: China,  India, Russia, Japan, Republic of Korea (South), according to FAOSTAT data from 2012.

 

Kale is a popular and incredibly versatile “superfood” that can be used in a variety of ways, including in salads, juices, smoothies, soups, pesto sauces, quiches, slaws, pastas, casseroles, pizzas, dehydrated kale chips, and more.