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  MG Manual Reference
Ch. 10, pp. 90 - 93

[Selected Crops: intro | asparagus | beans | broccoli | brussels sprouts | cabbage | cauliflower | sweet corn | cucumbers | eggplant | lettuce | melons | onions | peppers | potatoes | squash | tomatoes | herbs | herb use ]

Sweet Corn

Light: Sunny.
Soil: Tender annual
Fertility: Deep, well drained loam.
pH: 6.0 to 7.0
Temp: Warm (60° F to 75° F)
Moisture: Average.
Planting: Seed after danger of frost is past; extra sweet varieties should be planted when soil temperatures reach 65° F.
Spacing: 9 to 12 inches by 24 to 36 inches minimum of three rows side by side (preferably four rows) to insure good pollination.
Fertilizer Needs: Heavy feeder; sidedress when plants are 12 to 18 inches high with 3 tablespoons of 10-10-0 per 10-foot row.

Sweet corn varieties differ significantly in time to maturity and in quality, yellow, white, bi-color, standard and extra-sweet varieties are available. Most varieties planted are hybrids which have been bred for greater vigor and higher yields. A continuous harvest can be planned by planting early-, mid-, and late-season varieties, or by making successive plantings of the same variety when the previous planting is at the three leaf stage. Use only the earliest varieties if growing season is short. Sweet corn that matures during cool nights will almost always be the highest quality, since it has an increased sugar content.
Pollination is a very important consideration in planting sweet corn. Because corn is wind-pollinated block plantings of at least 3 to 4 short rows will be pollinated more successfully than one or two long rows. Good pollination is essential for full kernel development.
Most of the various types of corn will cross-pollinate readily. To maintain desirable characteristics and high quality, extra-sweet and standard sweet corn should be isolated from each other. A distance of 400 yards or planting so that maturity dates are one month apart is necessary to insure this isolation. Sweet corn plantings must be isolated from field corn and popcorn or ornamental corn as well. White and yellow types will also cross-pollinate, but the results are not as drastic.
The newly developed extra- or super-sweet types convert sugar into starch more slowly than standard varieties. They are not necessarily sweeter than just-picked old favorites (though some cultivars are), but they will retain their sweetness after harvest longer than usual. Super-sweet varieties may be less creamy than standard varieties due to genetic differences. This characteristic decreases the quality of frozen or canned super-sweet corn though newer cultivars of extra-sweets show improvement.
Some gardeners are interested in growing baby corn such as that found in salad bars and gourmet sections of the grocery store. Baby corn is immature corn, and many varieties are suitable, but Candystick, with its 1/4-inch diameter cob at maturity, is a good one to try, especially since its dwarf habit means that it takes up less space in the garden. Harvesting at the right time is tricky; silks will have been produced, but ears are not filled out. Experimentation is the best way to determine when to harvest baby corn.
It is not necessary to remove suckers or side shoots that form on sweet corn. With adequate fertility these suckers may increase yield, and removing them has been shown in some cases to actually decrease yield.
Mulching is a useful practice in corn growing because adequate moisture is required from pollination to harvest to guarantee that ears are well-filled. Since main crops of corn usually ripen during drier periods, it is especially critical to maintain soil water supplies, mulching reduces the need for supplemental watering and keeps the moisture content of the soil fairly constant. Most organic mulches are suitable; newspaper held down with a heavier material on top is an excellent moisture conserver in corn.
Normally, sweet corn is ready for harvest about 20 days after the first silks appear. Pick corn that is to be stored for a day or two in the cool temperatures of early morning to prevent the ears from building up an excess of field heat, which causes a more rapid conversion of sugars to starch. Of course the best time to pick is just before eating the corn; country cooks say to have the pot of water coming to a boil as you are picking the corn, husking it on the way from the garden to the house! This is an exaggeration, but with standard varieties, sugar conversion is rather rapid. Field heat can be removed from ears picked when temperatures are high by plunging the ears in cold water or putting them on ice for a short time. Then store in the refrigerator until ready to use. Extra-sweet varieties will also benefit from this treatment, but they are not as finicky.
Diseases: Stewart's wilt (bacterial disease spread by flea beetle); Smut (especially on white varieties) remove infected part; Stunt (transmitted by leafhoppers).
Insects: Corn earworm, southwestern corn borer, corn seed maggot, flea beetles, Japanese beetles (eat silks), corn sap beetles (damage kernels after husk is loosened or when ear is damaged by corn earworm).
Other: Birds eating seed, raccoons eating mature ears of corn, gardener's impatience (picking too soon). Cover unharvested ears with a paper bag to prevent insect or bird damage.
Cultural: Poor kernel development- failure to fill out to the top; caused by dry weather during silking states, planting too close, poor fertility (especially potassium deficiency), too few rows in block resulting in poor pollination. Lodging (falling over) from too much nitrogen.
Days to Maturity: 63 to 100 days.
Harvest: When husk is still green, silks dry brown, kernels full size, and yellow or white color to the tip of the ear. Harvest at the milky stage. (Test by puncturing a kernel with thumbnail. If a clear liquid appears, the corn is immature. If the liquid is milky, the corn is ready. If no liquid appears, the corn is over-ripe). Experienced gardeners can feel the outside of the husk and tell when the cob has filled out. Corn matures 17 to 24 days after first silk strands appear, more quickly in hot weather, slower in cool weather.
Approximate yields: 5 to 10 pounds (roughly 10-20 ears) per 10' row.
Amount to Raise: 20 to 30 pounds or about 40 to 60 ears per person.
Storage: Refrigerate immediately to prevent sugars from turning to starch; Cold (32° F), moist (85% relative humidity) conditions, 4 to 8 days, but standard varieties will become starchy after a few days.
Preservation: Frozen on or off the cob, canned.

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