If you live in the North, it's not too hard to grow corn that's "knee high by the Fourth of July," and if you live farther south you can easily beat that date. The advantage of early corn pays off if you want to sell it at a roadside stand. Choose an early variety like 'Earlivee', 'Early Sunglow' or 'Quickie'. Plan to plant four to six weeks before the last frost date in your area. It's a good idea to use treated seed to prevent damping-off and other diseases.
Plant the seed about 1 1/2 to 2 inches deep -- a little deeper than usual. If you want to, you can cover the rows with a plastic tunnel for extra heat or with chicken wire to protect the seeds from birds.
Corn germinates best at soil temperatures above 55° F and can't germinate in soil that's too cool, so the seeds may take longer to come up than you'd expect. After the first hot sunny spring day, however, you'll see the seedlings shoot up and take off.
When the seedlings are 8 to 10 inches high, give them their first dose of fertilizer. Side-dress with a balanced fertilizer and then water. Side-dress again when the plants are knee-high, and give a third nutrient boost when they tassel. Soon afterward you'll have the first local corn.
As a heat-loving plant, corn is easily set back during a cold spell, especially immediately after planting. Some gardeners like to protect their corn seeds and seedlings from cold weather by covering their rows or hills with plastic sheets or hot caps. This is one way to guarantee an early harvest of your early corn, but you may find it's more work than it's worth.
An easier solution to the threat of cold weather is to plant early corn deeper and use no fertilizer. If a corn seedling is zapped by cold weather, as long as the plant is less than 12 inches high, it will usually recover and start growing again. This is due to the location of corn's "growing point," the place where new growth begins.
Every vegetable plant has a growing point, and a frost-sensitive plant can be killed if its growing point is hit by a freeze. In the first weeks of growth, corn's growing point lies below the soil surface, protected from frost. Although it eventually reaches the soil surface and grows above it, this doesn't happen until the corn plant is about a foot tall -- about 21 days after planting, and that's quite a frost-beating edge. Naturally, if you fertilize, the plant will grow faster and be susceptible to frost that much sooner.
If you're planting early, relax for the first three weeks after planting. Mother Nature is providing the vital frost protection corn needs.
Gardening Without Fertilizer
You can raise corn without any fertilizer whatsoever (neither organic nor man-made) if you rotate it with edible cover crops of peas and beans and annual ryegrass. Peas, beans and other legumes have the ability to replenish some of the soil's supply of nitrogen. You may also need to add lime or sulfur to maintain the proper pH.
You'll grow the healthiest, most productive crops with the following two-year rotation sequence: first year -- an early edible crop of peas, followed by snap beans or soybeans, followed by annual ryegrass; second year -- one crop of sweet corn, followed by annual ryegrass.
The first year's cover crops yield a lot of peas and beans. Immediately after each harvest, till in the crop residues to add valuable organic matter and nitrogen to the soil. The cover crops are planted in a solid block, rather than in rows. The plants are lush and thick, shading the soil and blocking the weeds.
After you harvest the last beans in late summer, till under the plants and plant the third cover crop of annual ryegrass. This grass dies when the cold weather hits, and it mats to insulate the soil during the winter, making it warmer so soil life remains active longer.
Come spring, till the ryegrass under for additional organic matter, which helps condition the soil. The next crop, the sweet corn, produces beautifully in rich, naturally fertile, nearly weed-free soil.
Some gardeners mulch their corn to prevent weeds and to keep the soil moist. Although mulching can be beneficial in hot, dry climates, keep in mind that you'll need quite a load of mulch material -- hay, straw, leaves, peat moss, etc. -- to take care of a good stand of corn. As long as you give corn a steady supply of food and water, it really doesn't require much other care.
If you plant corn in hills or plant the rows too thickly, you'll have to thin out some plants to make sure the others have enough room to grow. Thin when the seedlings are about four inches tall.
The best time to thin is after a rain when the plants have dried but the soil is still moist. The plants pull easily from the soil without disturbing neighboring seedlings.
To thin, just pull up enough plants so that those remaining in the row or hill will be 10 inches apart. If you crowd your corn a bit -- about 8 inches apart -- don't worry, it should do fine; but if you're just getting the hang of raising corn, give your plants more room.