Corn seeds were first planted in North America as far as 200 B.C., according to North Carolina Cooperative Extension Service. While field corn is grown mostly for animal food and industrial purposes, such as making cooking oil and ethanol, sweet corn is produced mainly for human consumption. The American Indians introduced the sweet corn seed to European settlers as these early American colonists began settling in the New World. Papoon corn, which came from the Iroquois Indians in 1779, was the first corn kernel variety produced in America.
A corn seed, or kernel, is made up of three parts: a thin outer covering, an endosperm and an embryo. The outer covering consists of two layers: an inner testa (true seed coat) and an outer pericarp. The endosperm is mostly composed of starch and takes up almost 66 percent of the seed's volume, according to Purdue Horticulture. The embryo contains most of the corn's oil and is usually located on one side of the kernel, instead of in the center of the seed.
Different types of corn seeds vary in shape and size. Some corn kernels are only 1/8 inch long and have mostly a rounded shape, such as popcorn seeds. Others corn seeds can be as long as a half-inch and have a flattened-cylinder shape, notes Purdue Horticulture.
It takes an average of 100 to 140 days for a corn seed to fully ripen, according to Purdue Horticulture. On the other hand, some varieties ripen in only 80 days. Pollen shedding and egg fertilization occur about halfway through the ripening process.
Supersweet corn seed varieties are stunted and, therefore, don't sprout well in wet, cold soil. By waiting until soil is as warm as 65 degrees Fahrenheit, seeds are more able to germinate, reports the University of Illinois Extension. Sow these seeds more thickly and then thin them out, if needed. Using fungicide seed treatments also helps.
Plant in fields not containing harmful weeds, cautions North Carolina Cooperative Extension Service. Practice crop rotation because this limits the accumulation of weeds.
Isolate supersweet seed varieties from other types of corn seeds to ensure tenderness and sweetness. Supersweet varieties have weak pollen that can be easily supplanted by other corn seed varieties. This can cause a corn seed to develop into the tough, starchy texture characteristic of field corn. Corn is pollinated by wind, so an isolation distance can be 500 feet or more, notes the University of Illinois Extension.