Corn comes in many varieties. Though the origins of these are lost in time, it probably started as a cross between two now-extinct grasses.  One feature, however, remains constant: With no wild form to fall back on, all varieties of corn now require the intervention of mankind for their continued existence. Due to its pollination by the wind, it has always been incredibly easy to cross one variety of corn with any other.  Being so easy to breed, new forms to suit current needs are always being developed. This ease of crossing also means that the careless worldwide experiment to create genetically modified (GM) corn has, undoubtedly, already contaminated most of the world’s heritage varieties.

Historical Record

Popcorn is the oldest of the current forms of corn. It has such a tough skin that it conveniently explodes when the moisture trapped inside is quickly heated to produce steam. It has been a popular snack food for a very long time.

Dent corn, with a linear dent on its flat surface, probably led to its being considered the “mother grain.” Its starchy kernels can be roasted for snack food, simmered in stew, or coarsely ground into meal for Italian polenta, Romanian mamaliga, British hasty pudding, or American grits. It can also be wet-ground into flour for use in flatbreads such as tortillas.

Flint corn is a grittier, northern form of dent corn. It was primarily grown as animal feed, but has more recently been bred for providing glucose syrup. This is further refined to produce the cheap high fructose corn syrup that is now a ubiquitous ingredient in most North American processed foods.

Sweet corn first appeared as a natural mutation of a gene that causes the sugars in the immature ears to only gradually convert to stable starch. At first this was considered a drawback. But Peruvians determined this could be fermented into beer-like chichi, and American Indians determined that these could be preserved by slowly roasting the whole ears in the husks until the sugars were caramelized. In the 1850s, seeds-men bred this sweet corn into a popular new garden vegetable.

Types of Sweet Corn

All of the early sweet corns appear to be extinct. However, a few of their descendents are still commercially available. Country Gentleman is a very tall, 10-foot plant with the usual pair of 10-inch ears of corn. Its unusually delicious kernels are not in the usual straight lines, but in more interesting patterns. Canadian-bred Orchard Baby is a very short, 3-foot plant that produces many small 6-inch ears. Luther Hill is another delicious, garden-sized midget. This lives on as one of the parents of the still very popular Silver Queen. In the 1930s, Golden Bantam was the first yellow corn to become popular. (Yellow corn was previously considered fit only for animals.) Stowells Evergreen can be harvested immature to slowly mature out of season. This is done by pulling up the whole plant and hanging it upside-down for two to three months until the kernels become milky and sweet.

In the 1950s, researchers at the University of Illinois determined ways to slow down the conversion of sugar into starch even more. The older forms with a 12 percent sugar content would only remain sweet for an hour or so. These received an “SU” (for sugar) designation. The newer forms with 18 percent sugar could remain sweet for up to three days and received the designation “SE” (for sugar enhanced). In the 1980s, with the advent of long-distance shipping and year-round availability, another version became useful. This variety could produce 35 percent sugar and remain sweet for weeks (but become tough and chewy after one week). These corns received the designation “SH2” (because the dry seeds are shrunken and shrivelled). More recent developments combine all of these characteristics, so you might now see SU+, SU++, and SY designations in seed catalogues. For real corn flavour, just choose SU and perhaps SE varieties.

Quality Growing

Growing corn is quite different from any other garden vegetable. Instead of planting in lines, corn must be planted in square blocks. For complete pollination you will need a block of at least ten plants by ten plants. (Large plants require about 2 square feet each; so 200 square feet is the minimum; the older, small plants do fine with half this space.) Incomplete pollination results in missing kernels. Corn also requires warm soil to properly germinate: 10° C for SU, 14° C for SE, and 17° C for SH2 varieties. Corn requires high fertility, so an extra-large dose of compost helps to fill the ears completely and maximizes flavour. If you have a small block of plants, it might be worthwhile to shake the tassels every day while they are dropping pollen. And since corn does not tolerate competition, extra attention to weeding is necessary.  One more important consideration is that each variety must be separated by at least 300 feet to prevent cross-pollination which may adversely affect your crop. Alternatively the varieties should have a maturity date at least ten days apart. Or you can plant similar maturities at least ten days apart.

Given all of these impediments, you should choose an exceptional variety to grow. There are hundreds to choose from. I would choose one of the older, full-flavoured SU varieties; or if sweetness is important to you an SE variety will have some flavour. Most varieties now come in a yellow, a white, and a bi-colour version. (This will take some research because each will likely have an unrelated name.) There is little flavour difference between colours.

European corn borer and corn earworm are the main insect pests.  As soon as pollination is complete, dribbling a few drops of mineral oil down the silks, or wrapping an elastic band around the silks, can prevent the larvae from entering. Some growers have had success by cutting off the tassels as soon as pollination is complete. Raccoons are a more difficult pest to deal with.

About twenty-one days after you first see the silks, the ears are ready to harvest. To confirm they are ready, open an ear and puncture a kernel.  If a milky white liquid exudes, the corn is ready. The classic cooking instruction is to bring a pot of water to a boil, then head out to pick the ears. Equally as effective – and a little more practical – is to half-fill a bucket with water and ice. Chilled immediately, the freshly picked ears will remain perfectly sweet until dinnertime. SE varieties do not require this treatment but it is fun to do anyway.

Growing corn is a lot of work, but the results can be absolutely amazing. If this seems like too much work or requires too much space in your own garden, you can better understand that a fair price for a properly grown ear of corn should be at least a dollar; not the usual 25 cents.

Recipe

Spicy Grilled Sweet Corn with Feta and Herbs

David Cohlmeyer is the founder of Cookstown Greens (www.cookstowngreens.com), which grows and delivers premium vegetables and salad greens to many of Toronto’s most critically acclaimed restaurants, hotels and caterers.