CORN

Vitals

• Origins: Central America.

• Early archeological evidence: Tiny, fingernail-sized cobs with tassels dating back to 3600 BC were found in Bat Cave, New Mexico, and a series of cobs showing size increase from one-half inch to eight inches over a span of 5,500 years was found in the Tehuacan Valley of Mexico.

• Conflicting archeological evidence: Pot shards dating back to 2920 BC have been found in Ecuador with embedded kernels the size of modern ones.

• Climate: Corn is adapted to a variety of climates and growing seasons.

• Major producing countries: United States, China, Brazil.

Zea mays is the most genetically diverse, researched, manipulated, and industrially exploited food plant in the world. More than 500 million metric tons of the crop, also known as “maize,” are grown a year, half of it in the United States. Only one-fifth of all corn grown in the world is consumed by people. Two-thirds of the planet’s corn crop is fed to livestock, and the rest is used in many of the things that make our modern lives possible: adhesives, coatings, textiles, roadways, and countless other unlikely products.

Corn’s story is one of interdependence between plants and humans. At its beginning is teosinte , a wild grass that is itself a hybrid of two grassy plants. At its end is a giant grass that relies on its human cultivators for its reproduction. In between are tens of thousands of farmers selecting and cross-pollinating maize in their fields, initially in the Americas, and later also in Europe, Asia, and Africa.

It was with corn that researchers in the 1920s first began to use newly understood principles of genetics in plant hybridization, pollinating one crop with another that displayed a desired trait such as drought resistance or uniformity. Their ability to develop disease-resistant varieties with ears that could be easily harvested by machine prompted a revolution in agriculture. Soon after, growers of other vegetables followed suit, cross-pollinating all manner of vegetables to suit the demands of an agriculture that was making increasing use of technology.

Because of its structure, corn has also proved to be an excellent plant for studying genetics. Each kernel is the ripened fruit of a female flower, and each contains a genetically distinct seed, the tiny corn embryo inside arising from whatever genetic cross resulted in fertilization. This means that one ear with a hundred kernels can hold a hundred different varieties, and a researcher can study them all at once, on the same plant. Barbara McClintock used this quality to look at inheritance, and it led her to the discover of mobile genetic elements, or “jumping genes,” for which she won the Nobel Prize. Researchers continue her work and her cornfield at Cold Spring Harbor Laboratory in New York State.

Today, our vast knowledge of the corn genome allows scientists to create varieties geared to very specific needs. Many agriculture companies have developed their own breeds of corn by adding to them useful genes found in nature—genes for pest resistance, high yields, and other traits. These plants are called “genetically modified,” because the makeup of their genes has been changed slightly. Some farmers and environmentalists have raised questions about GM plants, saying that there are potential risks that outweigh the benefits of these crops. For more on this debate, see Three Ways to Make a New Plant and Why Save Seeds? articles.

Corn is very easy to save seed from, but it's very hard to keep as a pure variety if you are growing more than one kind in your garden. Corn is wind-pollinated, so plants should be separated by at least 1,000 feet (300 meters) if you want to grow more than one variety.

• Most corn is already quite hybridized and selected for specific traits, so many of the things you'd find desirable have already been brought out through plant breeding. But you can still look for the plants that most display the traits you’d like. Look at both the plants and the ears when considering which plants to save seed from.

• Corn is sensitive to inbreeding and can also self-pollinate. So save seed from as many different plants as you can.

• Ears are ready for harvest about four to six weeks after you would harvest them for eating. Pull the ears from the stalk, peel back the husks, and hang the corn in a well-ventilated place to dry for a few weeks.

• When they are dry, remove the seeds by holding the cob in one hand and twisting it in the other, catching the falling kernels in a container. Any silk or other chaff can be winnowed (blown away by sifting the seeds from one container to another outside in the wind).

Because corn is so hybridized, it might be hard to find good seeds to grow out for seed-saving purposes. You want to make sure the seeds are from what are called “open-pollinating” varieties. For a list of companies that sell these seeds, see our article Why Save Seeds?

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