Spinach, genus Spinacia, is a member of the goose-foot (Chenopodiaceae) family. It is an annual crop plant that is widely cultivated for its nutritious, dark green leaves. Spinach is thought to have originated in southwestern Asia and was known in Europe as early as the twelfth century. In the United States, California and Texas produce most of the country's spinach. Spinach is an excellent source of vitamins A and C, vitamin B12 (riboflavin), and many minerals, such as iron. As the food industry became more sophisticated in terms of nutritional research, marketing, and advertising in the first half of the twentiethth century, spinach became a popular vegetable because of its nutritional value, and because of the cartoon character "Popeye," who taught children to eat spinach so that they could become strong and healthy like him.
The best known species is Spinacia oleracea. Two varieties are grown extensively, one with smooth leaves and another wrinkled, savoy variety. Both of these can be purchased fresh at produce stores. In the food packing industry, the smooth-leaved type is usually canned or frozen before shipping, and the savoy variety is packaged and shipped fresh.
Spinach grows best in cool, temperate weather. Cooler, northern growing areas sow seeds in spring and fall, while warmer, southern areas grow spinach during the winter months. The growth period is usually about 40 days. As spinach plants develop and mature, a dense cluster of leaves form a rosette. When mature, a central, flowering stem grows, sometimes reaching a height of 3-4 ft (90-120 cm). Small flowers, which later produce seeds, grow in clusters in the axils of the stem leaves. The plants are picked while immature, and before the flower stem has started to grow. If grown during mid summer with hot weather and extended daylight, spinach plants develop the central stem too quickly (bolting), which draws growth and nutrition away from the leaves, which are the desired crop. To help avoid bolting, scientists have developed plants that are late bloomers. Crop damages are usually caused by pests such as aphids and leaf miners, or fungal diseases, such as blight and downy mildew, for which scientists have developed resistant varieties of spinach.
See also Plant diseases.
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