Kale and collards are among 3000 species of plants in the brassica or mustard family, most of which are edible potherbs. Originally from the area around the Mediterranean Sea they have become adapted to most of the world's temperate zones and even parts of the sub-arctic and tropical zones. The genetic structure of the plants allows for relatively frequent mutations and cross pollinations. This has led to a great variety of forms, such as cabbage, broccoli, cauliflower, Brussel sprouts, and kohlrabi, all of which developed from a common kale-like ancestor.
Kale and collards are the most nutritious of all the brassicas largely because they don't form heads, so their leaves are more fully exposed to sunlight. The cause of the dreaded disease scurvy (vitamin C deficiency) was discovered when the symptoms of it were quickly reversed in British sailors given lime juice. While citrus fruits are still thought of as a primary source of vitamin C, raw kale has nearly four times as much vitamin C as an equal weight of oranges or limes. It was kale and its close relatives in the 'Old King Cole' family, not limes that kept scurvy from decimating Europe. Now researchers are finding that regular eating of these plants may help prevent another scourge. Isothiocyanate, sulforaphane and other compounds in brassica family plants appear to have strong cancer prevention properties.
Always a food of the common people, kale and collards have supplied vitamins, minerals, protein, and antixodiants that protected us when it counted most. Whether in 'Colcannon', a potato and kale staple that nourished the beleaguered Irish peasants, or in the form of a thousand other soups, stews, and messes of greens, kale and collards have earned the right to be called "soul food".
- Collards and kale are extremely nutritious foods.
- Not only are kale and collards rich in calcium, but unlike many greens that contain oxalic acid, the calcium is very well absorbed. In fact, it has a higher bio-availability than the calcium in milk.
- They are among the most cold hardy of vegetables and can survive temperatures well below freezing.
- Ornamental forms of kale, called flowering kale, are easily integrated into edible landscaping schemes.
- They sprout quickly and are very easy to grow.
- The unopened flower buds of kale and collards make a tasty potherb similar to tiny broccolis.
- Can be easily grown over the winter in containers inside, or in simple greenhouses or coldframes
- Along with spinach, collards have the highest levels of the carotenoids lutein and zeaxanthin, and are the most strongly associated with a reduction in age-related macular degeneration (AMD) risk. About 13 million Americans age 40 and older have this disease, which gradually destroys the sharp, central vision needed for seeing objects clearly and for common daily activities such as reading and driving. It is more common than glaucoma and cataracts combined.
- Raw kale and collards contain several glycosinolate compounds that can prevent the body from producing thyroxine and lead to a condition of swollen thyroid gland known as goiter. These goitregens that limit the usefulness of brassicas as forage crops are destroyed by heat.
- Root rot is a common problem when plants are grown in waterlogged conditions, especially in the spring.
- Heavy feeders that require ample nitrogen and organic matter for good growth
- Need cool nights to thrive
- Popular red Russian kale is not a true kale. It is more closely related to turnips.
- A variety of tree kale raised at the TRIADES research center in Hawaii is a perennial that is adapted to tropical temperatures. It shares other kales' nutritional properties but rarely flowers, instead propagating from stem cuttings.
- Kale and collards are very frost hardy, but should be planted at least 6 weeks before the average first frost in the fall to give the plant time to build up energy reserves.
- Leaves of these plants taste sweeter after a frost because they protect their leaf tissues from freezing by converting some stored starch into soluble sugars. The presence of the dissolved sugar lowers the temperature at which the plant sap will freeze by several degrees. We generally prefer the flavor of the greens with the increased sugar content.
- Taller kale and collards varieties are often prone to lodging or falling over as they get very top heavy. 'Champion' and 'Hicrop' are two shorter more compact varieties of collards that don't have this problem.
- It is a good idea to plant brassicas in a different spot each year if possible to prevent a buildup of soil microorganisms that attack the roots.
- Kale leaves have become a popular garnish around salad bars and buffet because of their attractive dark green curly leaves.
- While the new inner leaves are the most tender, picking the older outer leaves and letting the new ones develop will result in far greater total leaf harvest.
- Typical planting density for commercial production is 30,000 60,000 plants per hectare.
- Shallow rooted plants benefit greatly from mulching to reduce drying of the upper layer of soil.
- Cabbage worms, one of the more serious pests, can be controlled by BT. This is a safe, biological control because it is a parasitic bacteria that is quite specific as to its host. It is often sold under the names 'Dipel' or 'Thuricide'.
Seeds for common varieties of kale and collards are usually available anywhere garden seeds are sold in the temperate zones. For more unusual varieties, such as walking stick kale, it may be necessary to go through mail order seedhouses. Johnny's seeds, Seeds of Change, and Shepherds seeds are examples of companies that carry a wider variety of kale and collard seeds.
Brassica oleracea var. capitata (cabbage); B. oleracea var. costata (couve or Portugese cabbage); B. oleracea var. italica (broccoli); B. oleracea var. alboglabra (chinese kale); B. oleracea var. botrytis (cauliflower); B. oleracea var.gemnifera (Brussels sprouts); B. oleracea var.gongylodes (kohlrabi); B. napus pabularia (red Russian kale); B. carinata (Ethiopian mustard); B. chinensis (pak choy); B. rapa (turnips); B. juncea (mustard); B. nigra (black mustard); B. japonica (mizuna)
There are about 3000 species in the Brassica or mustard family. Most of these wild species are edible but many are very pungent and fibrous.