Corn

Corn is a warm-season annual that should not be sown until soil temperatures reach about 60°F, since seed will not germinate below 55°F. It is grown in full sun in fertile, well-drained soil, and because it is wind pollinated, seed is sown in blocks of several short rows or hills rather than one long row, with a dozen or more plants needed for reliable pollination.

Watering: Corn is a heavy feeder that needs ample nitrogen and consistent moisture throughout growth, but water should be applied to the soil rather than over the plant to avoid interfering with pollination.

Weeding: Because corn roots resent disturbance, excess seedlings and nearby weeds are cut rather than pulled when thinning, and mulch is used once the soil has warmed to suppress weeds instead of cultivating around the shallow roots. Successive plantings every couple of weeks extend the harvest season.

Corn is subject to a number of insect pests, including European corn borer and corn earworm, both better managed by destroying old cornstalks in fall and by timing plantings early, and seedcorn maggot, which is discouraged by avoiding heavy manure or organic matter that attracts egg-laying adults. Diseases include rust and smut, along with Gibberella ear rot and maize dwarf mosaic virus; rust is limited by watering early in the day so foliage dries quickly and by spacing plants for good air circulation, while smut galls are removed by hand before they break open.

Nutrient stress shows visibly in the leaves: purple-tinged leaves signal a phosphorus deficiency, while pale green leaves indicate a nitrogen shortage.

Ears are generally ready to pick about three weeks after pollination, when kernels are in the sweet, milky stage that gives the best eating quality before the sugars begin converting to starch. If left on the plant past this point, corn moves into a drier "dough" stage as kernels lose water, which is the point at which corn intended for storage or grinding is allowed to fully mature and dry on the stalk. Seed saved from a corn crop remains viable for about two years.

Culinary: Corn is eaten fresh on the cob, and its kernels are boiled, roasted, grilled, or ground into cornmeal for breads and other dishes such as tortillas and Makki Ki Roti. Field corn is also used to make foodstuffs including corn flakes and cornmeal, and it is fed to livestock, while some specialty types are bred with waxy or high-amylose starches for particular food and industrial uses.

Medicinal: In traditional Chinese medicine, corn silk has historically been used for complaints affecting fluid retention, jaundice, and the urinary tract.

The earliest archaeological evidence of corn comes from Mexico's Valley of Tehuacan and has been dated to about 7,000 years ago, with the crop believed to have been first domesticated in southern or central Mexico. It became central to the Mayan, Aztec, and Incan civilizations, often grown alongside beans and squash in the companion planting known as the three sisters, before spreading to Europe, Africa, and Asia following European contact with the Americas.