Corn is known scientifically as Zea mays. This moniker reflects its traditional name, maize, by which it was known to the Native Americans as well as many other cultures throughout the world. Although we often associate corn with the color yellow, it actually comes in host of different varieties featuring an array of different colors, including red, pink, black, purple, and blue. Although corn is now available in markets year-round, it is the locally grown varieties that you can purchase during the summer months that not only tastes the best but are usually the least expensive.
Sweet corn may be divided into three distinct types according to genetic background: normal sugary (SU), sugary enhancer (SE) and supersweet (Sh2).
Standard sweet corn varieties contain a “sugary (SU) gene” that is responsible for the sweetness and creamy texture of the kernels. SUs are best suited to being picked, husked and eaten within a very short time. In the home garden, this is sometimes possible but not always practical. The old adage was “start the water boiling, run to the patch, pick and husk the corn, run back to the pot, cook the corn, and eat or process immediately.”
Sugary enhancer hybrids contain the sugary enhancer (SE) gene, that significantly raises the sugar content above standard SUs while retaining the tenderness and creamy texture of standard varieties. The taste, tenderness and texture are outstanding. SEs are the gourmet corns of choice for home gardeners because they contain the best qualities of both SU and Sh2 types. Fresh from the garden, virtually all current SE releases have eating quality that is superior to all other types. No isolation from standard SUs is necessary.
Supersweet hybrids contain the shrunken -2 gene and have a higher sugar content than the standard SU varieties. The kernels of the extra-sweet varieties have a crispy, tough-skinned texture and contain low amounts of the water-soluble polysaccharides that impart the creamy texture and “corny” flavor to other sweet corn varieties. Although the lack of creamy texture is not especially noticeable in fresh corn on the cob, it affects the quality of frozen and canned corn, as does the toughness of the seed coat. Unless corn must be stored, shipped or mechanically harvested, SEs are superior in eating quality to Sh2s.
Supersweets (Sh2) should be isolated from any other type of corn tasseling at the same time to ensure sweetness and tenderness. Their pollen is weak and easily supplanted by other types, which causes the kernel to revert to a form with the toughness and starchiness of field corn. Because corn is wind-pollinated, this isolation distance can be 500 feet or more, especially downwind.
In the Garden
Sweet corn requires warm soil for germination (above 55°F for standard sweet corn varieties and about 65°F for supersweet varieties). Early plantings of standard sweet corn should be made at, or just before, the mean frost-free date unless you use special soil-warming protection such as clear polyethylene mulch film.
For a continuous supply of sweet corn throughout the summer, plant an early variety, a second early variety and a main-crop variety in the first planting. For example, you may wish to select Sundance (69 days) for the first early variety, Tuxedo (75 days) for the second early variety and Incredible (83 days) for the main-crop variety. Make a second planting and successive plantings of your favorite main-crop or late variety when three to four leaves have appeared on the seedlings in the previous planting. Plantings can be made as late as the first week of July.
Plant the kernels (seeds) 1/2 inch deep in cool, moist soils and 1 to 1 1/2 inches deep in warm, dry soils. Space the kernels 9 to 12 inches apart in the row. Plant two or more rows of each variety side by side to ensure good pollination and ear development. Allow 30 to 36 inches between rows.
All sweet corns should be protected from possible cross-pollination by other types of corn (field, pop or flint). If you plant supersweet or synergistic sweet corn varieties, plan your garden arrangement and planting schedule so as to prevent cross-pollination between these varieties and with any other corn, including nonSh2 sweet corns. Supersweet varieties pollinated by standard sweet corn, popcorn or field corn do not develop a high sugar content and are starchy. Cross-pollination between yellow and white sweet corn varieties of the same type affects only the appearance of the white corn, not the eating quality.
Cultivate shallowly to control weeds. Chemical herbicides are not recommended for home gardens. Although corn is a warm-weather crop, lack of water at critical periods can seriously reduce quality and yield. If rainfall is deficient, irrigate thoroughly during emergence of the tassels, silking and maturation of the ears.
Hot, droughty conditions during pollination result in missing kernels, small ears and poor development of the tips of the ears. Side-dress nitrogen fertilizer when the plants are 12 to 18 inches tall.
Some sweet corn varieties produce more side shoots or “suckers” than others. Removing these side shoots is time consuming and does not improve yields.
Each cornstalk should produce at least one large ear. Under good growing conditions (correct spacing; freedom from weeds, insects and disease; and adequate moisture and fertility), many varieties produce a second ear. This second ear is usually smaller and develops later than the first ear.
Sweet corn ears should be picked during the “milk stage” when the kernels are fully formed but not fully mature. This stage occurs about 20 days after the appearance of the first silk strands. The kernels are smooth and plump and the juice in the kernel appears milky when punctured with a thumbnail. Sweet corn remains in the milk stage less than a week. As harvest time approaches, check frequently to make sure that the kernels do not become too mature and doughy. Other signs that indicate when the corn is ready for harvest are drying and browning of the silks, fullness of the tip kernels and firmness of the unhusked ears.
To harvest, snap off the ears by hand with a quick, firm, downward push, twist and pull. The ears should be eaten, processed or refrigerated as soon as possible. At summer temperatures, the sugar in sweet corn quickly decreases and the starch increases.
Cut or pull out the cornstalks immediately after harvest and put them in a compost pile. Cut the stalks in one foot lengths or shred them to hasten decay.
In the Kitchen
Traditionally, boiling is the way to prepare corn on the cob. However, it can be steamed, grilled, roasted, and even microwaved. When boiling sweet corn, do not add salt to the boiling water as it only serves to toughen the kernels as does overcooking. To shuck corn, pull the husks down the ear and snap off the stem at the base. Under cold running water, rub the ear in a circular motion to remove the silk or use a stiff vegetable brush. To remove corn from the cob, you will need a sharp paring knife.
Place the shucked ear on a plate, large end down. Starting at the tip of the ear, run the knife straight down to the stem end leaving about 1/4 inch of the kernel on the cob. This prevents cutting off the tough cob fibers. Rotate the ear and cut until all the kernels have been removed. Now, using the back of the knife, gently scrape down the entire cob to remove the milk left behind.
Freezing is the best method for preserving the quality of sweet corn. Although it cans fairly well, it must be processed in a pressure canner for extremely long periods of time. Corn can also be pickled into corn relish.
To Freeze Sweet Corn
Select only tender, freshly gathered corn in the milk stage. Husk and trim the ears, remove silks and wash in cold water.
Corn on the cob
Water blanch small ears (1 1/4 inches or less in diameter) 7 minutes, medium ears (1-1/2 inches in diameter or more) 9 minutes. Cool in an ice water bath for approximately the same amount of time as blanching. Cool completely to prevent a “cobby” taste. Drain and package in gallon-size zip closure freezer bags. Push excess air from the bags, seal and freeze. Leave space between each bag until frozen.
Whole Kernel Corn
Water blanch corn on the cob for 4 minutes. Cool promptly in ice water for 4 minutes. Drain and cut corn from the cob. Cut kernels from the cob about two-thirds the depth of the kernels. Package in zip closure freezer bags or rigid containers leaving 1/2 inch head space.