How to Grow Sweet Corn: The Complete Guide

Photo Credit
Pixabay
Botanical Name
Zea mays
Plant Type
Vegetable
Sun Exposure
Full Sun
Soil pH
Slightly Acidic to Neutral
Bloom Time
Summer
Flower Color
White
Yellow

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Planting, Growing, and Harvesting Sweet Corn

Catherine Boeckmann

How do we grow the sweet corn of our dreams—full, juicy, and oh-so-delicious? It’s disheartening when there are gaps left in our cobs’ kernels. Corn needs to be planted properly for optimal pollination. Here’s how to plant, grow, and harvest sweet corn in the garden.

About Sweet Corn

Sweet corn is a tender, warm-season annual crop that produces ears of yellow, white, or bi-colored kernels. Native to the Americas, sweet corn has been cultivated for thousands of years; it’s famous as one of the Three Sisters—corn, beans, and squash—grown by Native Americans.

A long, frost-free growing season (60 to 100 frost-free days) is necessary to grow and harvest corn. Don’t be tempted to sow too early, though. Mid to late spring is just fine once any chance of frosts is long gone.

And corn is a grass! A member of the Poaceae family, corn relies on wind, not bees or insects, to pollinate its flowers. This is why we plant corn in blocks of short rows instead of long, single rows. 

Types of Sweet Corn

For a continuous supply of sweet corn, plant early, mid-season, and late varieties or plant every 2 or 3 weeks.  

Have you ever had the intensely disappointing experience of tucking into a juicy-looking sweet corn cob only to find it tastes bland? This is the number one reason why paying a little bit more for your seeds really pays dividends. Hybrid or F1 varieties of sweet corn may cost a bit more, but they’re worth every penny, yielding cobs with a superior flavor, especially if you pick one of the supersweet types. Varieties bred for sweetness hold their taste for longer too, but the sooner you cook them after picking, the better.

Learn more about the different varieties of corn below. 

Read Next

Planting

The most common reasons for slow growth include poor light levels, not enough moisture, or a lack of nutrients. Plant in full sun (at least 6 to 8 hours of direct sunlight). Soil needs to be consistently moist (though well-draining),as corn tends to suck up a lot of water. Corn is a hungry plant, so it’s important to enrich beds with lots of organic matter, such as garden compost (ideally in the fall).

When to Plant Corn

  • Most gardeners sow corn directly in the garden soil (versus indoors) so that their sensitive roots aren’t disturbed when transplanting.
  • Corn is very sensitive to frost; do not plant soil temperature is at least 60°F (16°C), or 65°F (18°C) for super-sweet varieties. Usually, this is 2 or 3 weeks after the last frost in spring. See our Planting Calendar for corn based on average frost dates.
    • If you live in an area with a shorter growing season, choose an early variety that will mature well before the first fall frost. The ground can be warmed by a black plastic cover; sow seeds through holes in the plastic.
  • A couple of weeks after planting your first round of corn, plant another round in order to extend the harvest.

Corn in the garden

How to Plant Corn

  • To speed germination, moisten seeds, wrap them in moist paper towels, and store them in a plastic bag for 24 hours. 
  • Because corn is wind-pollinated, it’s essential to plant in a block, rather than a single row. For decent pollination, we recommend a modest block of, say, 10 to 50 plants. This maximizes the chances of the pollen released from the male tassels at the top of the plants drifting down into contact with the female silks lower down. Incomplete or inconsistent kernel development, with the cobs only partly or sporadically filled, is down to poor pollination. The silks protruding from the end of each cob are responsible for carrying the pollen down to the kernels. One strand connects to one kernel, so for complete fill, every strand of the silk must be pollinated.
  • Sow seeds about 1½ to 2 inches deep and 12 inches apart in rows 2½ to 3 feet apart. Don’t plant too close together or you run the risk of disappointingly small cobs.
  • You may choose to fertilize at planting time with a general purpose (10-10-10 fertilizer); corn is meant to grow rapidly. 
  • Water well at planting time.

Sowing Corn Indoors

If you’re going to start seeds early, sow the seeds in pots under the protection of a greenhouse, hoop house, or cold frame. This means you can begin sowing three to four weeks before your last frost date, giving you a head start on corn sown outdoors—a huge advantage for areas with shorter growing seasons.

Sow eight to ten seeds half an inch deep into four-inch-wide pots, or sow two seeds per module in a plug tray and remove the weakest of the two seedlings when they emerge. Keep the potting soil moist as they grow on.

Harden off the plants as your recommended planting time approaches by placing them outside for increasingly longer spells over the course of about a week. Plants should be at least six inches tall by the time they’re transplanted outdoors.

Check out this video for great tips on growing juicy corn:

Growing

  • Consistent moisture will encourage bigger, fatter ears of corn, so it’s hard to over-emphasize the importance of this. Keep corn well watered, as it has shallow roots and can become stressed by drought. About 2 inches of water per week is sufficient; water more if conditions are especially hot or if your soil is sandy. If the soil remains dry, soak the soil again. When watering, aim at the base of plants to avoid problems with fungal diseases.
  • Mulch helps to reduce evaporation around the plants.
  • Corn’s roots are shallow and can easily be damaged by hoeing. Instead, weed your corn by hand for as long as you’re still able to get between the plants without damaging them.  Then, apply several inches of mulch.
  • Corn sometimes produces aerial roots a few inches above the soil. These are not meant to absorb water or nutrients but rather to stabilize the tall stalk. If this happens, mound soil up over the roots to keep them covered, or just cover the whole area with a mulch of compost, which will help feed the plants, too. 
  • Support stalks in windy places. Mounding the soil around the base of 12-inch-tall plants will help. If you do notice plants getting rocked about in the wind, consider tying them to stakes. 
  • Wind pollination is critical to developing full cobs of kernels. To help this along, gently shake the stalks of the plants every few days for as long as the tassels are viable to increase the chances of every silk being pollinated.  Mornings are best. Learn more about corn pollination, including how to hand-pollinate to guarantee pollination success.
  • Watch for signs of nitrogen deficiency (yellowing leaves) and respond with quick side-dressings of a nitrogen-rich fertilizer such as fish emulsion. 

Note: Tillers, or “suckers,” are secondary shoots that may develop low on the stalk later in the season. They do not adversely affect the main stalk.

Types

Types of Sweet Corn

There are four main types of hybrid sweet corn: sugary (su), sugar-enhanced (se), shrunken (sh, sh2), and synergistic (sy). Each one contains a different level of sucrose, changing the flavor and texture of the corn.The type of corn will be listed right on the seed packet.

It’s important to be aware of which type of corn you’re growing—not only because of the sugar content, but also due to how easily the types can cross-pollinate. If the wrong combination of types cross-pollinates, the ears that are produced may be of subpar quality.

  • Sugary (su) sweet corn is the classic sweet corn. Sugary varieties grow vigorously and are stress resistant. The kernels aren’t too sweet and are said to have a “traditional” taste. However, the sugars in sugary sweet corn quickly turn to starch after the ears are picked, so they need to be eaten right after picking. Do not plant near shrunken or synergistic types.
  • Sugar-enhanced (se) sweet corn is slightly sweeter than sugary varieties. They keep their sweetness for a longer period of time after harvest (a few days) than sugary varieties. They grow well with few issues. Do not plant near shrunken types.
  • Shrunken (sh, sh2) sweet corn—also called “supersweet”—are the sweetest varieties, containing two to three times more sugar than sugary varieties. The sugar in their kernels lasts even longer after harvest (up to a week) than the other types, but kernels tend to be more crunchy and not taste as “corny.” Shrunken types are also more finicky overall. Do not plant them near any other types; hybrid kernels turn out starchy and tough.
  • Synergistic (sy) sweet corn combines sugar-enhanced with one of the other two types to create varieties that have the best of both worlds. Synergistic types tend to have very sweet, tender kernels with a good taste and some synergistic varieties can keep up to a week after harvest. Do not plant near sugary or shrunken types. 

Recommended varieties include:

  • ‘AԳ’: sugar-enhanced variety, good taste. White kernels.
  • ҵdz󾱱’: midseason, normal-sugar variety. Yellow kernels.
  • ‘Luther Hill’: dwarf, normal-sugar variety. Produces 4- to 6-inch ears on 4- to 5-foot stalks. White kernels. Grow at least nine dwarf plants in a block of three or four rows.
  • ‘Silver Queen’: normal-sugar variety. Resistant to some bacterial diseases. White kernels.
  • ‘Sweet Sunshine’: supersweet variety. Disease resistant and high yield. Yellow kernels.

Corn can be a feast for the eyes, too! Look for these ornamental varieties:

  • ‘Glass Gem’: Sporting multi-colored, semi-transparent kernels, this is a favorite for kids.
  • ‘Painted Mountain’: Looking for the classic “maize” colors? This variety has a great diversity of natural tones.  

Harvesting

  • The warmer the air, the more quickly corn matures. It is usually ripe about 15 to 23 days after silking and sooner if temperatures are exceptionally high.
  • When two ears grow on a stalk, the upper ear matures 1 to 2 days before the lower one.
  • At harvest, ears should be rounded or blunt, not pointed, with tassels turning brown and kernels full and milky.
    • To test, pull down some husk and pierce a kernel with a fingernail. If it’s white, or milky, it’s ready. The milk stage is brief; in hot weather (over 85°F/29°C), sweet corn is at peak for only 1 to 2 days, so check it frequently. Corn harvested a few days after milk stage will not be as sweet.
  • Pull ears downward and twist to remove from stalk.
  • Sweet corn varieties (except for supersweet varieties) lose their sweetness soon after harvest. Immediately after picking, prepare the ears for eating or preservation.
  • Prepare for eating or preserving immediately after picking. Enjoy your harvested corncobs as soon as you can. The quicker they’re cooked, the sweeter they will be!
  • If immature corn suffers a late-season frost, the plants and cobs can be damaged and result in the death of the plant or poor-tasting corn.

Corn cob on the plant

How to Store Corn

Gardening Products

Wit and Wisdom

  • Baby corn is produced from regular corn plants that are harvested early, while the ears are immature. Regular sweet corn, sugar-enhanced sweet corn, and supersweet corn varieties can be used, along with a few varieties that are specific for baby corn.
  • A cornstalk grows slowly until it reaches about 24 inches; then it grows 3 to 4 inches per day in hot weather!
  • Different traditions have arisen as to the best time to plant corn. Many lunar gardeners plant when the Moon is waxing to encourage vigorous, healthy growth. However, according to another tradition, it is said that corn planted under a waning Moon grows more slowly but yields bigger ears. Learn more about gardening by the Moon!
  • If your corn shucks harder than usual, prepare for a cold winter.
  • Corn is one of the Three Sisters; its growing style pairs perfectly with beans and squash. Learn more about companion planting.
  • Corn is great for eating but also has so many other uses including medicinal. Learn more about corn for natural health.
  • Learn more fun, witty facts about corn.

Pests/Diseases

Corn Pests and Diseases
Pest/DiseaseTypeSymptomsControl/Prevention
AnthracnoseFungusYellow/brown/purple/black spots on leaves; sunken, dark spots on stems; spots may develop a salmon-pink, gelatinous mass; eventually, rot; in corn, tops die back and stalks rotDestroy infected plants; choose resistant varieties; provide good drainage; avoid overhead watering; apply compost; use mulch; rotate crops
Corn earwormsInsectOn corn, eaten silks and kernels; excrement; larvae also attack tomatoes and other plants, eating fruit/pods/leaves/flowersRemove caterpillars; apply vegetable oil to point where silks enter ears a week after silks first emerge; select corn varieties with tight husks; grow an early variety; add native plants to invite beneficial insects; till soil in fall; spray Bt
Cucumber beetles (spotted)InsectHoles in leaves; plants stunted/die; larvae feed on roots; may spread bacterial wiltHandpick; mulch heavily; use row covers; destroy plants infected with bacterial wilt
CutwormsInsectWilting; severed stems of seedlings just above or below soil line; whole seedlings disappearHandpick; in spring before planting, cultivate soil to reduce larvae; wrap a 4-inch-wide collar made from cardboard or newspaper around each stem, sinking 2 inches into soil; weed; use row covers; destroy crop residue
EarwigsInsectMany small holes in leaves/stems; corn silks eatenTrap in tuna can filled with 1/2 inch of fish oil and sunk in soil such that edge is slightly above ground level; remove plant debris
DeerMammalChewed stalks (especially on young plants); chewed earsScatter human-scented items, coyote urine spray, or blood meal around plants; enclose corn with fence (at least 8 feet tall)
Downy mildewFungusYellow, angular spots on upper leaf surfaces that turn brown; white/purple/gray cottony growth on leaf undersides only; distorted leaves or corn tassels; defoliationRemove plant debris; choose resistant varieties; ensure good air circulation; avoid overhead watering
Flea beetlesInsectNumerous tiny holes in leaves, like birdshot from a shotgunUse row covers; mulch heavily; add native plants to invite beneficial insects
Japanese beetlesInsectLeaves skeletonized (only veins remain); in corn, damage to husks/kernels/silk; grubs feed on rootsHandpick; use row covers; plant tansy near infested plants to lure beetles away
RaccoonsMammalBroken stalks; half-eaten, missing earsScatter human-scented items, coyote urine spray, or blood meal around plants
WirewormsInsectSeeds hollowed; seedlings severed; stunting/wilting; roots eatenTrap by digging 2- to 4-inch-deep holes every 3 to 10 feet, fill with mix of germinating beans/peas or potato sections as bait, cover with soil or a board, in 1 week uncover and kill collected wireworms; sow seeds in warm soil for quick germination; provide good drainage; remove plant debris; rotate crops

Recipes

Hartwell Farm Corn Pudding
Corn Custard
Corn and Black Bean Pitas
Summer Corn Cakes
Summer Corn Salad

Cooking Notes

  • If too much hot pepper or spice has been added to a soup or stew, adding a can of sweet corn can help.
  • Popcorn is also a favorite snack if you have leftover kernels. Learn how to make homemade popcorn here.
Vegetables
About The Author

Catherine Boeckmann

Catherine Boeckmann loves nature, stargazing, and gardening so it’s not surprising that she and The Old Farmer’s found each other. She leads digital content for the website, and is also a certified master gardener in the state of Indiana. Read More from Catherine Boeckmann
 

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Comments

David, We must be perfectly honest with you: After the research you say you have done, you have much more knowledge about corn than we do! But we will concur with you, based on the (il)logical comparison to peaches, with which we have some knowledge (but, it must to said, not much luck). Peach growers are advised to remove/prune small fruits to allow a smaller but better harvest. We think that the same would apply to corn. And it seems to apply to other plants, such as melons and pumpkin. After all, if the plant puts its energy into the remaining “fruit” (or ears, in this case), wouldn’t it be as good as it can be?! Assuming every other aspect of the growing conditions are favorable, of course. We say, trim the ears off those stalks! And, if you feel it might be of value, leave a few stalks alone; don’t trim them, and see, come fall, which method seems most productive.

And let us know how this goes, would you?

CarolinaGardener (not verified)

7 years 7 months ago

I know it's not Recommended to start Sweet Corn indoors, but in recent years I have seen it in market pack for sale as transplants And questioned why at the time. BUT Last year the crows got most of my seed. Would planting seed in the netted expanding peat disks 2-3 weeks before time to plant outdoors stunt the plants? I have an adequate light setup for tomatoes and peppers, etc. I think it would at least let them germinate, Could I plant them at 4 inches high without problems, or will I fail to get corn if I do?

Just leave the corn plants alone. The size of the cobs will depend on how fertile the soil is and the water you apply. I plant my corn in good rich soil. I apply some fertiliser down each side of the row when plants are about 12-18" high and I then hill the soil up the plant. A good watering each second day. Cobs 8-9" long. Qld Australia.

Hi! I too am from the Carolina and have been toiling in the garden for over 20 years. I always get my crops up in a rather unconventional way. I use the method of indoor to outdoor transplanting on beans, corn, tomatoes, etc. by getting them up in 16 FL. Oz Styrofoam cups using a mixture of 50% Jiffy Seed Starter soil and 50% Bacto Soil. I use a toothpick and poke plenty of holes in the bottom as well as the sides. Not only are the many tiny holes for water drainage but they also provide ample amounts of excess oxygen to the roots ( something the conventional means of planting does not provide ). Once everything is sprouted and growing good at around 7 to 8 inches ( given there's no fear of another frost ) I go ahead and transplant them outside. When transplanting plants or for that matter anything you need to make sure to not damage the roots which will sometimes stunt the plants growth. To do this simply water the the cups and let them soak up the water ensuring that the grow medium isn't too dry in turn resulting in a compact cup shaped plug of root and soil. Never transplant in the middle of the day. Best to do this process either early on in the day or later in the evening but regardless of the time always, always, always remember to adequately water the plants once they're in the ground. Transplanting has always been my method of choice because you take away all the unexpected variables that nature can throw at you. Hope this was helpful!

Hello, I've grown sweetcorn on my UK alottment for the last two years with the following slightly different methods:
Year 1: Sowing seeds in small hand made paper pots approx 1.5inch diameter, germinating in dark very warm cupboard. Out onto window sill, to get the light, as soon as the shoot shows through the compost. Keep on the window sill until about 2 inches tall. Transplant into 3 inch pots and back to the window sill until about 5-6 inches tall. Then out to small 'cold frame' in the garden until 16 or so inches tall. Then the weather was warm enough for them to go out into the ground on the alottment.

Year 2: Sowing seeds in 3 inch pots, germinating in dark very warm cupboard. Out onto window sill to get the light as soon as the shoot shows through the compost. Keep on the window sill until about 5-6 inches tall. Then out to small 'cold frame' in the garden for a couple of weeks to get them used to the cooler temperatures. Then out to our 'poly tunnel' at the alottment (very warm enclosure) for a few weeks. Then, when they were 16 inches or so and the weather was warm enough, they went into the ground on the alottment.

Windows in the back of the house have light until mid-day, ones in the front have sun later in the day so no more than 50% daylight for each set - I wonder what they would be like if they had sun all day. (temps 15-20 C)
Cold frame in the garden has direct sunlight for only 2/3 day with direct sunlight the temp rises to 30 C+. (I hope I don't forget to open the top when it's sunny - it got to 54 C one day just a month ago and I almost lost my tomatoes...)

Lots of indoor growing for us due to lower temps earlier in the year. Plenty of corn both years - first year we grew 40 plants, year 2 was 70 plants, this year we're going for a round hundred.

A lot of varying info but I wanted to show you how hardy they can be with temps and transplanting. I still have sweetcorn in the freezer from last year and I have just potted my first seeds for this year. Good luck, Rob.

Mike (not verified)

5 years 9 months ago

I grow corn in Qld Australia. Late summer (Feb) to early summer (Dec). Temps can range from summer 20 min to 34 max to winter 4-10 min to 22-25 max in winter. No frosts. I sow direct into damp soil with a light watering and do not water for 3-4 days, then only a light sprinkle. Corn grows really quickly. I use to plant corn seedlings between 2-6" high and would have to pull the plants apart to plant them - many bare rooted - no soil around the roots. Plant late afternoon. Good watering the first week and away they went.

The success of transplanting corn depends on several factors, including temperature, light, soil fertility, variety, container depth (to allow the seedlings to grow deep roots), giving seedlings time to harden off, not allowing them to grow too much before transplanting (2 to 3 weeks is likely OK), etc. However, it has been done with success. You may find the following article, by the Vermont Cooperative Extension, helpful, about one commercial grower’s experience.
http://www.uvm.edu/vtvegandberry/factsheets/transplantingsweetcorn.html
Good luck!

 

At one time, I used a product called "Stanley's Crow Repellent" which came in a small tin can and it resembled a thin tar-like substance. You coated the seed with it and the crows wouldn't touch it. I found it at Agway. It had an EPA registration number, but it was cancelled in 1986 from what I can find.

I use "Bill's Crow Repellent". I comes in 12 gauge and 20 gauge! :)

We run a string over the top of the corn rows until the corn is several inches high. The birds won't go under the string to get the plants.