Corn isn't difficult to grow but it needs rich, well-drained soil in full or nearly full sun. Where these conditions are lacking, it can be grown in a raised bed well amended with compost. Add plenty of fertilizer or organic material to any soil: corn is a very heavy feeder. You'll need 10 centi-metres of fresh compost or well-decomposed manure, or a fertilizer rich in phosphorus and potassium rather than nitrogen (4-6-8, for example) at recommended rates (these vary; read the label). Always plant corn to the north of other vegetables so it doesn't overshadow them.
Corn will not germinate in cold soil. In climates where soil warms up slowly, put down black plastic mulch at snow melt to speed up the process. Many seed suppliers treat corn seeds with fungicide to help prevent rot under cool conditions. Plant treated seed when soil temperature reaches 16°C. Wait until soil temperature reaches 21° before sowing untreated seed of sugar-enhanced corn, usually not until early June in most of Canada. Supersweet corn is even more cold-sensitive: wait until soil temperature reaches 24° before sowing even treated seed. In areas with less than 70 frost-free days, or where summers are cool, you can start corn indoors in peat pots about four weeks before the last frost date.
Corn's taste can be affected by neighbouring plants. The supersweets, especially, take on a starchy flavour if pollen from feed or sugar-enhanced corn reaches them. If you're planting more than one type, avoid cross-pollination by spacing blocks of corn at least 7.5 metres apart.
The only wind-pollinated common vegetable, corn must be planted in blocks of at least four rows rather than in single rows so pollen reaches neighbouring plants. Ears won't fill out if pollination is poor. For added insurance, once male flowers (tassels) have formed at the tops of the plants and the female flowers (silks) appear, shake the plants twice a day until the silks turn brown, allowing pollen to drop onto the silks below.
You'll get more corn in less space if you forget traditional rows and plant equidistantly (as per the square-foot gardening method in the June/ July 2001 issue): two or three seeds sown 30 centimetres apart in all directions.
In most parts of Canada, only one crop of early corn is possible. Sow seeds about three centimetres deep (two for supersweets) and water well to initiate germination. When plants sprout (four to seven days in warm soil, up to three weeks in cool soil), thin to the sturdiest plant per cluster; keep it watered and weeded. Corn's shallow roots can be damaged by hoeing, so mulch to keep weeds down. In windy areas, especially where soil is sandy, hill up the plants' bases with 10 centimetres of soil when they're about 30 centimetres tall so they don't blow over.
Insect problems are minor in most parts of Canada. The first sign of corn borer, a type of caterpillar, is usually a small hole in the stalk surrounded by sawdust-like frass (excrement). Squash the pest by squeezing the stalk below the hole before it works its way into the ear and eats the kernels.
Corn earworm lays its eggs on the silks; the larvae then work their way down into the husk and eat the immature kernels. The tight husks of modern corn varieties don't allow easy entry, but to be sure, wrap an elastic band tightly around the tip of the ear as soon as the silks appear. Then, even if the corn earworm makes it into the ear, it will damage only the uppermost kernels, which can be cut off.
Raccoons, squirrels and deer are far more serious pests, usually showing up at harvest time and stealing the crop overnight. Repellents such as deo-dorant soap hung around plants on the outside of the patch or baby powder sprinkled over the leaves (reapplied after each rainfall) sometimes work; more drastic measures such as motion-detecting sprinkler devices or electric fencing cost more than the crop is worth and still aren't foolproof.
Diseases aren't usually a major problem in home gardens, especially if you rotate your corn crop each year (a four-year cycle is sufficient). Corn smut is a wind-borne fungus that causes a misshapen grey growth to form on the ears, usually affecting only one or two ears per patch. But a week or two of rain at the wrong time—when the silks are receptive to pollen—will ruin the crop.