These 'Florida Broadleaf' mustard greens in Steve's winter vegetable garden are ready for picking.
Leaf mustard is a cool-season annual, usually grown for its variable, glabrous, rather thin basal leaves which are eaten raw or cooked like spinach. As day length increases, mustard bolts up with a 3 ft (0.9 m) stalk supporting bright yellow flowers that soon develop into sickle-shaped green seed pods. Several varieties have been named, and many cultivars have been selected, especially in China where B. juncea has been developed into a remarkable array of different vegetables. The most popular cultivars grown in the US for mustard greens are 'Southern Giant Curled', which has 15 in ( cm) elongate leaves with frilled, crumpled margins, and 'Florida Broadleaf', which has flat, oval leaves to 2 ft (0.6 m) long and 1 ft (0.3 m) wide, and is easy to clean. Several newer cultivars have been developed which are said to be slower to bolt. Among the many Asian cultivars are 'Green-in-Snow', which is smaller with pale green leaves, and often used in stir-fry or pickled; 'Osaka Purple-Leaved' which has mild-tasting purple-red leaves with white veins to 26 in ( cm) long, and is often used raw in salads; and 'Red Giant' which has dark red, crinkled leaves and white stems that are pickled. 'Tai Tau Choi' is grown for its roots which are similar to turnips. 'Cha Tsoi' is grown for its peculiar swollen stems with knobby bulges that are preserved in salt and pressed flat until most of the juice is removed. 'French Brown', 'Burgonde' and 'Tilney' are grown in Europe for the seeds which are made into pungent, brown, stone-ground, French and German mustard sauces.
Location Brassica juncea is a tetraploid - it has double the number of chromosomes normal for the genus. It apparently originated in Asia by hybridization between B. rapa (a variable species which includes turnip, Chinese cabbage, pak choi, and broccoli raab) and B. nigra (black mustard, the species generally grown for the seeds from which the yellow condiment is made). Leaf mustard has been cultivated in Asia and Europe for thousands of years. It probably was first domesticated in central Asia and the Himalayas. Some cultivars are grown in India, China and Japan for the oil extracted from the seeds. Others are grown for the leaves, roots, stems or flowers. In much of Europe, B. juncea has replaced B. nigra as the source of commercial mustard seed. Leaf mustard has escaped cultivation and become established as a weed in disturbed sites in North America.
Mustard greens are one of the easiest vegetables to grow. They can be planted a little before last frost in spring or after the hottest weather in autumn. In zones 8-11 mustard greens are grown in autumn and winter. In north Florida, I plant mustard in September or October and sometimes a second crop in January. By April they have pretty much petered out and gone to seed. Mustard greens are big enough to pick 30 days after planting from seed. Remove individual outer leaves and you can continue harvesting from the same plants throughout the season. In cold weather mustard greens have almost no pests, but warmer weather will bring on the aphids and cabbage worms. Mustard greens grow so fast, though, you can usually harvest plenty before the bugs make them too unsightly to be appetizing. If you do have aphids (usually on the underside of the leaves), just wash them off under the cold water tap before cooking.
Light: Does best in full sun, and okay in partial shade. Moisture: Does best with regular water. Larger plants become more drought tolerant. Hardiness: Mustard is a cool season, half-hardy annual. It can withstand temperatures as low as 20ºF (-4ºC) without damage. However, it cannot stand temperatures above 85ºF (29 ºC) or so, and will quickly bolt and flower as the days become warmer. Propagation: All of the mustard cultivars are grown from seed.
In Europe and the United States, mustard greens are eaten raw in salads or cooked as a potherb, like spinach. Mustard greens are tangier than spinach, collards and kale, and have a sharp, peppery flavor that is enhanced with a sweet, mild vinegar. We usually mix milder collards and kale with sharper turnip greens and mustard and cook in a steamer over boiling water. I like them with a little butter and salt and pepper; many people like to spice them up with hot chile pepper vinegar, and traditional southern cooks boil mustard greens with salt pork, bacon or ham. Be sure to serve cornbread to mop up the "pot likker."
In Asia, some kinds of mustard are pickled (called hum choy and sajur asin). Leaves and stems are also used in stir-fry and added to soups and stews. The seeds are very pungent and used to season meats and other dishes. Powdered seeds are used to make brown mustard, which is spicier than the American yellow mustard made from B. nigra. An oil made from mustard seeds is used to pickle foods in Kashimiri and Bengali cooking.
The taxonomy of the edible species in the genus Brassica is fascinating and complex. Gardeners have selected an astonishing diversity of different vegetables from a few original species. Here is a partial listing:
B. hirta - white-flowered mustard, grown for oil and greens
B. juncea - leaf mustard, mustard greens, brown mustard
B. napus - rutabaga, Siberian kale, rape-seed (from which canola oil is made)
B. narinosa - broad-beaked mustard, eaten raw or cooked
B. nigra - black mustard is grown for seeds that are made into the popular hot dog condiment