How to Grow Sweet Corn

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Sweet corn is a annual that prefers to be planted once the temperature of the soil reaches 60 degrees Fahrenheit or higher, which comes about one month after the last threat of frost. If sweet corn seeds are placed in soil that is cool and wet, the seeds have a greatly reduced chance of germination. Any that do sprout will almost certainly exhibit stunted growth. This heat-loving plant prefers air temperatures between 70 and 95 degrees Fahrenheit. Depending on the variety being grown, the temperatures, water availability and sun exposure, sweet corn usually takes 60 to 100 days from seed to harvest.

This grain, which is a member of the grass family, reaches four to 12 feet in height and typically produces two ears on each grass-like stalk. The tassels that form at the top of each plant contain the pollen, which falls onto the thread-like pistils that top each potential ear of corn to fertilize them. Each of these silky strands is connected to a single kernel of corn. Therefore, the fullness of each ear depends strongly on the thoroughness of pollination, which is usually done by the wind. When most people wonder how to grow sweet corn, they fail to consider that assistance with pollination is often necessary for optimal results.

Sweet corn can take on a variety of colors ranging from white, yellow and red to a mottled combination of colors. In most cases, sweet corn will only produce one to two ears per stalk, but some dwarf varieties can produce three to four.

How to Grow Sweet Corn

It’s recommended that you start between 12 and 20 plants per member of your household if you want to enjoy corn throughout the season. To facilitate healthy growth, plant the seeds in rich, loamy and well-drained soil with a high organic matter content. Ideally, the soil’s acidity should lie between 5.8 and 6.8, a bit on the alkaline side. Adding compost prior to planting increases levels of nitrogen, of which sweet corn is a heavy feeder.

Some people start their sweet corn seeds indoors about two to three weeks before the threat of last frost. However, this requires a moderate investment in fluorescent lights and bulbs, which must be kept no more than six inches above the seedlings at all times to ensure sturdy growth. You can expect your seeds to germinate within two weeks if you keep them at 75 degrees Fahrenheit consistently, but germination rates may not be optimal. Because of the tedium involved, people who aren’t familiar with how to grow sweet corn may prefer to start their seeds in the ground at the appropriate time of year. To ensure a steady supply of this delicious vegetable, plant successive crops two to three weeks apart until late summer or early fall.

If you’re planting your sweet corn outside, sow your seed two to four inches apart to form blocks as opposed to a single long row. This formation lends itself to the best chances of plentiful fertilization. You may also wish to consider planting two or more seeds per spacing to ensure adequate germination rates and full rows. After sprouting, thin your short variety seedlings to one foot to 18 inches apart, or 18 inches to two feet for taller ones, once seedlings are half a foot in height. Leave only the seedlings with the strongest and healthiest appearance. If you crowd your corn, it will result in excellent foliage production, but ear production will be poor or nonexistent.

As much as sweet corn likes hot weather, it also requires considerable and consistent moisture in order to grow properly, but preferably not from overhead. When watering, water around the bases of the plants to prevent wilting and fungal infections and to discourage pests. Watering from the bases becomes particularly important once the plants’ tassels appear and their ears begin to develop silk. Watering from the bottom of the plants prevents the valuable pollen from being washed off and wasted. Because corn requires large amounts of nitrogen, it’s recommended to feed your plants every three to six weeks with an aged compost or nitrogen-rich plant food. If you find that the leaves of your plants are yellowing, it’s a sign that they need more nitrogen. If they’re turning purple, the weather is either too cold or there’s a deficiency of phosphorus. Poor or no kernel production indicates too little potassium, poor pollination or overcrowding.

Pests aren’t terribly common with sweet corn, but they’re troublesome enough that you’ll want to take steps to avoid them. If you don’t wish to use pesticides, companion planting is an effective way to discourage unwanted guests. Such plants include tansy, potatoes, peas, cucumbers, beans, squash and pumpkins.

To care for your sweet corn, weeding is of the utmost importance as these plants will steal valuable water and nutrients and stunt corn’s growth. Since sweet corn is a vegetable with shallow roots, try to avoid tilling too deeply into the soil. If scavenging by birds is a concern, you can cover your corn ears with paper bags after they’ve been sufficiently pollinated.

While pests are not a huge issue for the average sweet corn grower, there are some that may be a menace. These include wireworms, flea beetles, corn earworms, cutworms, corn borers and even ants. The best way to rid your plants of these nuisances is to pick them off by hand and kill them. Earworms leave their eggs on the ears’ silky strands. The resulting larvae move down into the ears to eat the developing kernels. Adding a drop of vegetable oil to the tip of each ear suffocates these pests. You can expect corn borers to bore into the stalks of the plants and kill them by depriving them of nutrients. Prevent them by keeping plant debris cleaned up. Rats, mice, squirrels and raccoons are also frequent corn pests. Keep them out by installing traps or fences or spraying the ears with a cayenne pepper solution.

After 60 to 100 days depending on the variety and weather, your sweet corn will be ready to harvest. When the husks covering the ears become a deep green, the silky threads turn a light brown and the kernels are plump and juicy, the corn is ready to pick. Each plant will likely only yield two ears. In most cases, harvest occurs around 20 days after the appearance of the silks. It’s recommended to harvest your sweet corn in the morning and to immediately place them into ice-cold water in order to preserve their texture and sweetness.