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How to Plant, Grow, and Harvest Sweet Corn

How to Grow Corn
Growing corn

Sweet corn is a warm-season annual. It is one of the most popular home garden crops and one of the most widely planted commercial crops. Sweet corn is grown for its juicy, plump, sweet-flavored kernels. Corn can be eaten steamed, boiled, or roasted.

In addition to sweet corn, other types of corn include popcorn, flint corn, flour corn; flint corn is (Zea mays var. indurata; also known as Indian corn or sometimes calico corn is used in ornamental decorations); flour corn (Zea mays var. amylacea) is a variety of corn with a soft starchy endosperm and a thin pericarp; Zea mays everta, is the only type of corn to actually pop.

Sweet corn is a summer crop. It is best planted in late spring after the soil temperature reaches 60°F (16°C), usually two or three weeks after the last frost in spring. Corn planted out of season in cold, wet soil is unlikely to germinate.

Here is your complete guide to growing sweet corn!

Sweet Corn Quick Growing Guide

  • Corn grows best in air temperatures from 60° to 95°F (16-35°C).
  • Corn requires 6 to 8 hours of direct sun each day.
  • Corn can take from 60 to 100 days to reach harvest depending upon variety and the amount of heat during the growing season.
  • Corn is a tender annual and a member of the grass family that can grow from 4 to 12 feet (1.2-3.6m) tall.
  • One to two ears of corn form on the side of each tall, green, grass-like stalk.
  • Flowering tassels form at the top of each stalk; pollen falls from the tassels onto silky threads growing from each ear below. Each silk is connected to an unfertilized kernel.
  • Each ear of corn forms as many kernels as the number of silks that were pollinated. (Tassels are the male flowers of the corn plant. Kernels and ears are the female flowers.)
  • Kernels of sweet corn can be yellow, white, black, red, or a combination of colors.
  • A large corn variety may form one or two harvestable ears on each stalk.
  • A dwarf variety may form two or three harvestable ears per stalk. When pollination does not occur the stalk will produce only a cob.

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Corn Yield. Plant 12 to 20 corn plants per household member.

Where to Plant Sweet Corn

  • Plant corn in full sun.
  • Corn grows best in loose, well-worked, well-drained soil with a pH of 5.8 to 6.8. Adjust the soil pH if necessary before planting.
  • Add aged compost or aged manure to the top 8 to 10 inches of the planting bed before planting corn or add aged compost to the planting area in the autumn before planting.
  • Adding plenty of organic matter to the planting area will ensure good drainage. Rich soil–that is soil rich in organic matter–will also ensure rapid growth.
Corn planted in garden
How to Grow Corn: Corn is a tender, warm-season annual that is best planted after the soil temperature reaches 60°F (16°C), usually 2 or 3 weeks after the last frost in spring.

Sweet Corn Planting Time

  • Corn is a tender, warm-season annual that is best planted after the soil temperature reaches 60°F (16°C), usually 2 or 3 weeks after the last frost in spring. Corn will germinate in soil as cool as 50°F but germination will be delayed.
  • Corn requires 60 to 100 frost-free days to reach harvest depending upon variety and the amount of heat during the growing season.
  • Corn grows best in air temperatures from 60° to 95°F ((16-35°C).
  • Corn seed germinates in 10 to 14 days at 75°F (24°C), but the rate of germination may reach only 75 percent.
  • Corn planted in cold, wet soil is unlikely to germinate.
  • Outdoor corn seed sowing can begin 3 weeks after the last frost in spring. Check seed packet for the cold tolerance of the variety you want to grow.
  • Start corn indoors 2 to 3 weeks before the last frost in spring for transplanting 2 to 3 weeks after the last frost. If your season is long enough, plant successive crops every two to three weeks. Place seed trays or pot on a seed starting heating mat and under a grow light.

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Corn planted in rows

Planting and Spacing Sweet Corn

  • Sow corn 1 to 1½ inches (2.5cm) deep. Sow pathogen-free seed.
  • Plant seeds 2 to 4 inches (5-10cm)  apart in short, side-by-side rows to form a block, rather than one long row. A square block of plants with 10 or more plants in each row is best for to ensure pollination. A square block of corn plants is often called a corn patch.
  • You can also grow several plants on mounds or inverted hills.
  • Planting in a block or clump will help ensure pollination.
  • Thin plants from 12 to 18 inches (30-45cm) apart for short varieties and 18 to 24 inches (45-61cm) apart for tall varieties once plants are 4 to 6 inches (10-15cm) tall.
  • Corn planted too closely will require more water and fertilizer and may offer a smaller yield.
  • For a continuous harvest, succession plant corn every two weeks or plant early, midseason, and late varieties at the same time.
  • Sweet corn seed is viable for 1 to 3 years if stored in a dry, airtight container.

More tips: Corn Seed Starting Tips.

Watering Sweet Corn

  • Keep corn evenly moist and regularly watered.
  • One inch of water per week (6 gallons per square yard) in average summer weather; more in very hot weather.
  • Corn grows fast in hot weather and requires an even supply of moisture to avoid wilting.
  • Avoid overhead watering particularly when tassels appear; water hitting the tassels at the time of pollination can reduce the number of kernels on a cob.
  • Water-stressed corn will produce ears with missing kernels.
  • Use the finger test to know if you should water: stick your index finger into the soil, if it comes away dry, it’s time to water.

Fertilizing Sweet Corn

  • Add aged compost and aged manure to planting areas in the autumn before planting.
  • Corn is a heavy feeder; it needs plenty of nitrogen user.
  • Side dress corn with aged compost or compost tea when stalks are 10 inches tall and again when they are 18 inches tall and a third time when they tassel.
  • You can also side dress corn with nitrogen-rich blood meal, feather meal, aged chicken manure, alfalfa meal, or cottonseed meal.
  • Add “green manure’ such as clover or vetch into the crop rotation for areas where you plan to plant corn.

More tips: How to Increase Your Corn Crop.

Sweet Corn Companion Plants

  • Good companions for corn are potatoes, peas, beans, cucumbers, pumpkins, and squash.
  • Do not plant corn with berries or pole beans.

Sweet Corn Care

  • Weed corn early to avoid competition for water and nutrients. Corn is shallow rooted so avoid deep cultivation.
  • Crowding stimulates lots of silage, but no cobs.
  • To protect corn from birds cover ears with paper bags after pollination.
  • Poor kernel development can be the result of poor pollination, too few plants resulting in poor pollination, overcrowding, or a potassium deficiency in the soil.
  • If stalks are purple looking there is likely a phosphorus deficiency.

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Container Growing Sweet Corn

  • Corn can be grown in a large container but is not a practical choice for container growing because pollination requires several plants.
  • Plant 5 or 6 seeds in a large five-gallon container.

Sweet Corn Pests

  • Corn can be is attacked by cutworms, wireworms, flea beetles, corn earworms, and corn borers. Look for pests and handpick and destroy them.
  • Corn earworms are moth larvae. Moth eggs hatch on developing silks; later the small caterpillars will follow the silks down into the ears, where they feed on the tips. Place a drop of mineral oil inside the tip of each ear to coat and suffocate earworms.
  • Corn stalk borers–European corn borers–are purple and white moth larvae that will tunnel into stalks and ears to begin feeding. Handpicking is the best control. Keep the garden free of debris where borers and earworms can live. Use row covers to exclude beetles.
  • Corn flea beetles are tiny black beetles an eighth of an inch long that transmit Stewart’s wilt; they chew leaves. Use floating row covers to exclude corn flea beetles.
  • Armyworms are striped moth larvae that feed on corn foliage, especially in spring. Remove armyworm by hand to spray with Bacillus thuringiensis (Bt), an organic moth larvae control.
  • Corn leaf aphids are blue-green sap-sucking insects that attack corn foliage. Aphids can disrupt pollination and stunt plant growth; a sharp blast of water will knock them from plants; beneficial insects such as lady beetles, green lacewings, and syrphid flies will eat aphids.
  • Corn rootworms are cream-colored beetle larvae less than a half inch long; the adult beetles eat corn silks; pick beetles off by hand.
  • Cutworms feed on roots and stems of corn seedlings; these pests live in the soil near plants; overturn the soil to uncover them; use paper collars to protect seedling stems from cutworms.
  • Flea beetles are tiny black and bronze leaf beetles 3/8 inch long that will chew on leaves; exclude flea beetles by covering young plants with row covers.
  • Japanese beetles are metallic copper with green insects that will chew corn silks; larvae are white grubs that grow to an inch long; control with Bacillus thuringiensis (Bt) or by hand picking.
  • Seedcorn maggots are white fly larvae a quarter inch long; they feed on seeds especially in cooler, wet weather. Turn the soil before planting to expose larvae to the cold.
  • Slugs can defoliate young plants; use an iron phosphate bait to kill these pests.
  • Wireworms are click beetle larvae about a half to 3 inches long; turn the soil ahead of planting to expose these pest to killing cold temperatures.
  • Raccoons and many rodents will also attack corn. Use traps or fences to exclude these pests.

Sweet Corn Diseases

  • Corn is susceptible to smut, a fungus disease, and Stewart’s wilt, a bacterial disease. Corn smut will turn kernels gray or black and cause kernels to swell. Destroy affected plants, and do not replant in the same place for two years. Smut spores can survive in the soil for two years.
  • Stewart’s wilt is a bacterial disease spread by flea beetles. Stewart’s wilt will cause leaves to yellow and plants to become stunted. Plant disease-resistant varieties and control flea beetles by placing wood ash or agricultural lime around plants.
  • Corn is also susceptible to Anthracnose, rust, leaf spot, and leaf blight. Crop rotation is the best way to avoid the spread of pathogen diseases; avoid planting corn in the same spot every year; a four-year crop rotation is best.

More help with corn problems: Corn Growing Problems: Troubleshooting.

Corn near harvest
Corn is ready for harvest when ears turn dark green, silks turn brown,

Sweet Corn Harvest

  • Corn requires from 60 to 100 days to reach harvest depending on the variety and warm weather. A corn plant typically produces two ears per stalk; some varieties are higher yielding.
  • Corn is ready for harvest when yellow silks turn dark brown, and kernels are soft and plump; squeeze a kernel with your fingernail– if the juice is milky, not clear, the ear is ready for picking.
  • Harvest usually comes about 20 days after the silks appear.
  • Pick corn by grabbing the ear and giving it a sharp downward twist.
  • Each stalk of corn will produce one or perhaps two harvestable ears of corn.
  • Harvest corn in the morning when the kernels are full of moisture and plunge ears immediately into cold water to preserve sweetness.
  • Harvest flint corn just before the first frost.
  • Harvest popcorn and flour corn when the kernels are hard and glossy.

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Storing and Preserving Sweet Corn

  • Corn is best eaten fresh.
  • Keep sweet corn in their husks until ready to cook.
  • Corn will keep in the refrigerator for 2 to 4 days; wrap the unopened husk in damp paper towels.
  • Blanched corn on the cob can be frozen for 3 to 6 months.
  • Store flint corn, flour corn, and popcorn in a dry place. Peel back the husk and hand the ears to allow kernels to dry further.

More tips: How to Harvest and Store Corn.

Sweet Corn Kitchen Use

  • Sweet corn is served cooked either on or off the cob.
  • Kernels can be removed from the cob before or after cooking. Remove kernels with a sharp knife.
  • Sweet corn can be steamed, boiled, or roasted. Husks can remain on corn ears when they are roasted.
  • Raw kernels can be added to soups, mixed with vegetables, stews, and relishes.
  • Cooked kernels can be added to salads, omelets, pasta, risotto, salsa, soups or added to a vegetable medley.
  • Uncooked kernels can be frozen or canned.
  • Flint corn (Zea mays var. indurata; also known as Indian corn or sometimes calico corn) is used to make hominy.orn is used in ornamental decorations.
  • Flour corn (Zea mays var. amylacea) is a variety of corn with a soft starchy endosperm and a thin pericarp used to make flour.

Sweet Corn Varieties

  • Early season, yellow corn: ‘Bodacious’ (75 days); ‘Earlivee’ (69 days); ‘Early Sunglow’ (63 days); ‘IlliniChief’ (75 days); ‘Sugar Buns’ (72 days); ‘Tuxedo’ (74 days).
  • Midseason, yellow corn: ‘Golden Bantam’ (83 days); ‘Golden Cross Bantam’ (90 days).
  • Late season, yellow corn: ‘Kandy Korn’ (89 days)
  • Early season, white corn: ‘Platinum Lady’ (85 days); ‘Sugar Snow’ (68 days)
  • Midseason, white corn: ‘Alpine’ (79 days); ‘Argent’ (82 days); ‘Divinity’ (75 days); ‘Pristine’ (79 days)
  • Late season, white corn: ‘How Sweet It Is’ (87 days); ‘Silver Queen’ (94 days); ‘Stowell’s Evergreen’ (100 days)
  • Early season, bi-colored corn: ‘Athos’ (67 days); ‘Double Gem’ (75 days); ‘Quickie’ (65 days); ‘Skyline’ (73 days); ‘Sugar and Gold’ (67 days)
  • Midseason, bi-colored corn: ‘Butter and Sugar’ (73 days); ‘Clockwork’ (78 days); ‘Honey and Cream’ (78 days);
  • Late season, bi-colored corn: ‘Pilot’ (90 days).
  • Space-saving varieties: ‘Baby Corn’ (65 days); ‘Golden Midget’ (65 days).

Recommended Varieties

  • ‘Avalon’ bears tender white kernels on ears to 8 inches long; resistant to northern corn leaf blight, southern corn leaf blight, and southwestern corn leaf blight; matures in 82 days.
  • ‘Big N’ Tender’ bears a mix of white and yellow kernels on ears to 8 inches long; resistant to northern corn leaf blight and Stewart’s wilt; mature in 79 days.
  • ‘Cafe’ tender yellow kernels on ears to 8 inches long; fast-growing; a good choice for early planting in cool soil; resists Stewart’s wilt and rust; mature in 68 days.
  • ‘Calico’ heirloom flint corn with yellow, brown, white, purple, red, and blue kernels to 6 inches long; use as ornamental corn; matures in about 100 to 105 days.
  • ‘Dakota Black’ open-pollinated variety with dark red kernels on ears to 7 inches long; use as ornamental or for popping; matures in 95 days.
  • ‘Jerry Peterson Blue’ open-pollinated flour corn; make blue flour; ears grow to 8 inches long; matures in 105 days.
  • ‘Glass Gem’ open-pollinated flint corn; kernels are various colors on ears grow to 8 inches long; use as ornamental or for making cornmeal or popping; matures in 110 to 120 days.
  • ‘My Fair Lady’ sweet corn with white and yellow kernels on ears that grow to 8 inches long; mature in 78 days.
  • ‘Solstice’ bicolor sweet corn; resistant to northern corn leaf blight; matures in 68 days.
  • ‘Sugar Buns’ sugar-enhanced sweet corn with creamy yellow kernels on ears to 7 inches long; resistant to northern corn leaf blight and Stewart’s wilt; 70 to 80 days to maturity.

More tips: Corn Varieties: Best Bets and Easy-to-Grow.

More About Corn

  • Common name. Corn, sweet corn, maize
  • Botanical name. Zea mays subsp. mays (sweet corn)
  • Family: Poaceae (grass family)
  • Origin. Central America
  • Types of corn: sweet corn, popcorn, flint corn, flour corn; flint corn is (Zea mays var. indurata; also known as Indian corn or sometimes calico corn is used in ornamental decorations); flour corn (Zea mays var. amylacea) is a variety of corn with a soft starchy endosperm and a thin pericarp; Zea mays everta, is the only type of corn to actually pop.
  • Corn is the most widely planted crop in the United States and much of the world.
  • Corn that is picked fresh when kernels are plump and juicy is a vegetable. Corn that is picked when kernels are hard and dry is considered a grain.

More tips: Sweet Corn Growing Tips

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Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. Harvesttotable.com has more than 10 million visitors each year.

Comments

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  1. Hi, I planted 6 corn stalks in a crate. It’s as tall as me already. 2 months old. And no corn in sight. Temperature was as high as 105′ but I put protection over it. What could be the problem?

    • Perhaps too much nitrogen fertilizer; feed the plants with a dilute solution of fish emulsion; you can also water them with a solution of 1 tablespoon Epsom salt mixed in a gallon of water–this will help flowering.

  2. We harvested our corn to early and the cob looked like a building built by the architect Gaudi! Some kernels were formed somewhere not. But these were also grown in containers. My first try at container growing corn . we haven’t opened the rest of the cob‘s that are in the fridge. We had an extreme heat wave and all of our tassels were already purple but turned brown so I believe I may have pulled my ears too early. I will find out when we open the others. The miniature corn was perfectly formed, very sweet and very tender. Plus I was wondering if blue corn has a purpleish color stock or am I looking at a deficiency? The corn variety is drought resistant corn from the Southwest and I live in California. I don’t know if that has any bearing on the growth either.

    • The corn with missing kernels was not designed by Gaudi; it was insufficiently pollinated. Corn is commonly pollinated by the wind. There are two flowers–male (tassels) and female (silks). Tassels emerge from the top of the corn plant, then open to disperse pollen on the silks which emerge lower, from the immature corn ear. If pollen fails to fall on a silk, it will not be pollinated and no kernel will follow. Ensure the corn receives a breeze when flowers appear; you can also give each plant a gentle shake. A blue corn variety may have a tinge of purple or blue but that can also be a sign of insufficient nitrogen or phosphorus; you might want to test the soil.

  3. I’m trying something this time that I haven’t tried before. I planted my corn in the garden 4 different dates so I would have fresh corn coming on all thru the summer. so far the early corn made good and already harvested the 2nd planting is now coming on, the third planting will be about 4 weeks before it comes on and the 4th planting is about 5 inches tall now. Will the 4th planting have time to make for the table???

    • If you have 60 to 70 more warm days in your growing season, the fourth crop will mature. The number of crops you can grow is only limited by the length of the growing season which varies from one part of the country to the next.

    • Yes, cantaloupe like squash can be grown with corn. Allow the vines to cover the ground around corn; the vines will shield the soil from sun and help conserve soil moisture–which corn will use to help ears grow big.

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