Corn History and How it Grows
by National Gardening Association Editors
All about corn's past and the different types available.
Corn is authentically American. A member of the grass family, it was first domesticated from a wild grain several thousand years ago by Aztec and Mayan Indians in Mexico and Central America. The first corn was a loose-podded variety that looked like the seed head at the top of wheat stalks. The kernels were small and each covered by a hull. Central and South American peoples came to depend so heavily on corn -- or maize -- that they devised some of the earliest calendars just to keep track of their corn planting and harvesting schedules.
Eventually, corn's popularity spread to North America. By the time the first European settlers arrived on this continent, corn was the chief food crop of the native Indians. The colonists quickly learned how to grow corn, and they enthusiastically adopted the new staple. In fact, much of the early fighting that took place between the settlers and the Indians was over cornfields. The stakes were high; losing a cornfield meant losing your food supply.
Back then, people raised what's now called field corn. Some corn was eaten fresh, but most of the harvest was cooked in fried cakes, breads and puddings, dried for winter storage or ground into cornmeal and corn flour. Field corn was also used for livestock feed, as it is today. Sweet corn varieties weren't developed until the 1700s.
Over the years, cross-pollination during cultivation caused genetic changes that transformed corn into the shape and size we now know. Today, corn is still more popular in this country than anywhere else in the world. There are thousands of strains of corn, with more than 200 varieties of sweet corn alone.
All the varieties can be divided into four basic groups: field corn, sweet corn, popcorn and ornamental corn. There are many varieties of field corn; some are favorites of gardeners and farmers who eat them as roasting ears. These can be "dent" or "flint" corns, both of which can also be dried and ground for homemade meal. Flint corn has a hard-shelled kernel, and it does well in the cooler climates of New England and Canada. Dent corn is somewhat hard-shelled, and the top of the kernel forms a characteristic dented shape when the ears are mature.
Popcorn, another hard-shelled variety, contains very hard starch that expands when heated until the kernel pops. For all the corn groups, kernel texture, shape and flavor are often governed by the starch and sugar content, and this differs with each variety. These variations are exactly what make our favorite fresh corn varieties the soft-shelled, moist and sweet-tasting ones; that's why they're known as sweet corn.
How Corn Grows
Whether you're raising field corn, popcorn or sweet corn, they all grow basically the same way. Once the seed or kernel is planted in an inch or two of soil, it germinates in 5 to 12 days, depending on the variety and the soil temperature. Corn won't germinate if the soil temperature is below 55° F. It germinates fastest in soil that's 68° to 86° F.
After the seed sprouts, it sends down a taproot and starts to develop its first leaves. These leaves resemble blades of grass when they sprout.
As it grows, corn develops a thick, fibrous stalk and many flat, pointed leaves. The stalk can grow as tall as 15 feet, depending on the climate and variety. The roots of each plant grow down 3 to 5 feet and extend about 1 foot or so to each side of the stalk. Some of the roots develop above the ground. These are called "prop roots," and they serve as natural supports for the tall stalks.
When the stalk reaches about two-thirds its full height, its reproductive process starts. The plant first develops straw-colored tassels near the top. These are the "male" flowers of the plant. About three days after corn tassels, the silks or stigma of the "female" flowers appear lower on the stalk. These long, threadlike silks develop from the newly formed ears of corn. Each silk corresponds to a single kernel within the ear, and each kernel must be pollinated in order to have a completely filled ear. The tassels contain pollen that falls down and is carried to the silks by the wind. The tassels produce much more pollen than will ever be needed, and the silks flutter about in the wind to catch drifting pollen. The surface of each silk has tiny hairlike receptors to hold the pollen once it lands. It then travels down the silk to the kernel area, where fertilization occurs.
Although it's possible for a corn plant to fertilize itself, the pollen usually travels to the silks of neighboring plants. To ensure complete fertilization, it's best to plant corn in several short rows or blocks rather than long, narrow rows.
Even with nature's added insurance, pollination can be hampered by weather, soil conditions and poor fertility. That's why some ears may be completely filled and others may not.
Each corn plant generally produces one or two ears, except for special multieared varieties. Once pollination takes place, the kernels begin to develop on each cob. It usually takes about three weeks from silking for the first ears to be ready to harvest. The weather plays a big part here. The kernels develop fastest when the weather is hot and there's plenty of water. If it's too cool or too dry, the harvest will be delayed.
The next stages of corn's growth determine the flavor and texture of the kernel. Here you have a great deal of control, because it's often just the timing of the harvest that counts.
Newly formed corn kernels are full of liquid or "milk." The milk stage doesn't last long in most varieties, because the plant's natural goal is to convert that sweet liquid into starch. (If the seed were allowed to continue its life cycle, the starch would be stored and used later as food to sustain the new plant.)
However, the milk stage is the peak harvesttime for sweet corn, and gardeners who can successfully judge their corn's growing progress are well rewarded.
If corn isn't harvested during the milk stage, the starch-making process goes ahead, and the inside of each corn kernel becomes more solid, losing its sweet taste. This is called the "dough" stage.
The final stage of kernel development occurs if you don't harvest the stalks or if you dry them for winter storage. Sweet corn seeds become wrinkled and transparent as the natural starches eventually lose their water content.
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