Corn — or maize, as it’s known in much of the world — is the most planted crop in the United States. In agriculture, corn is grown for human consumption, spirits, animal feed and even fuel and disposable containers. In the home garden, this warm-season crop is usually grown for one reason: to enjoy the unmatched flavor of a fresh-picked ear of corn. If you want to grow corn in your garden, here is everything you need to know.
You can also download my How Do I Grow Corn? one-sheet and keep the free resource handy for your reference.
Corn is a grass just like wheat and oats, though corn stalks are typically much taller — as high as an elephant’s eye, as they say. Corn that stays in the field until the kernels are hard and dry is considered a grain while corn that is picked when the kernels are plump and juicy is considered a vegetable.
Home gardeners grow sweet corn more than any other type of corn, but some also grow popcorn, flint corn and flour corn.
If your desire is to enjoy corn on the cob, you want to grow sweet corn. Corn on the cob can be steamed, boiled or roasted and then served with salt and butter or a variety of spices. Elote, or Mexican street corn, is corn on the cob prepared with cotija cheese, mayonnaise, crema and chili powder. Sweet corn can also be removed from the cob to be enjoyed on its own, in a medley with other vegetables and in soup, chili or salsa.
Flint corn comes in all the colors of the rainbow. It’s the corn you often see used in fall decorations, but it’s edible too. It’s the type of corn that’s traditionally used to make hominy, which, in turn, is used for making tortillas.
Flour corn is the type of corn most often used to make corn flour, while popcorn — you guessed it — is grown specifically for making popped corn.
Where, When & How to Plant Corn
Corn grows best in loamy, well-drained soil under full sun — six to eight hours of unfiltered sunlight daily. Prepare the garden bed by turning a generous amount of compost and/or aged manure into the top 8 to 10 inches of soil. Amending the soil will help the garden drain properly while also improving fertility, which is vital for a successful corn crop. Keep on top of removing weeds that are competing with corn seedlings for water, nutrients and space.
The soil pH should be somewhere between 6.0 and 7.0, which is slightly acidic. When the pH is in the correct range, the plants will be better able to take up nutrients from the soil. A soil test will let you know the pH level and how to adjust it, if necessary. This usually calls for adding lime to the soil but you won’t know how little or how much lime to add until you have had your soil tested. Contact your local cooperative extension about having a soil test done. The results will also reveal any micronutrient deficiencies that need to be resolved with soil amendments.
Use pathogen-free seed from a trusted source. Corn seed can remain viable for one to three years if stored in ideal conditions.
Corn can be direct sown in the garden or started indoors. The time for indoor seed starting is four weeks before you plan to transplant the seedlings outside. Because corn thrives in warm weather, don’t try to start corn any earlier than the instructions on the seed packet recommend. The correct starting time differs from one variety to the next. Some varieties are more tolerant of cold than others and some mature more quickly than others. There is no one-size-fits-all start date for planting corn in your region.
For indoor seed starting, sow seeds 2 inches deep in sterile seed-starting mix, one seed per cell. Corn will germinate in soil that is as cool as 50°F, but it will take three weeks. The optimal soil temperature range is 60° to 95°. In that range, expect emergence in 12 days or fewer. A seedling heat mat will raise the temperature of the seed starting mix for faster germination. Keep the seedling under a grow light so they will not stretch out in search of sun.
Prior to planting the seedlings outdoors, harden them off. Put seedlings out for just a half-hour on the first day and add more time outdoors each day for a week until they are ready to handle eight hours of direct sunlight daily.
Corn seedlings can also be purchased from garden centers in spring. While this is more convenient than starting seeds on your own, it is more expensive and there will be fewer varieties available compared to purchasing seeds.
If direct sowing, refrain from planting until the soil temperature has reached 50°. An inexpensive soil thermometer can give you a quick reading.
Plant one seed or seedling every 4 to 6 inches in rows spaced 30 inches apart. Because corn is wind pollinated, one row of corn is unlikely to produce ears. Several short rows — instead of one or two long ones — will pollinate readily.
If you wish to prolong your harvest window, plant more rows two weeks after your initial planting.
Avalon is a sweet corn with tender white kernels. The ears grow to 8 inches and this variety is resistant to northern corn leaf blight, southern corn leaf blight and southwestern corn borer. Avalon matures in 82 days.
Big N’ Tender has a mix of white and yellow kernels on 8-inch ears. The plants grow up to 8 feet tall and have resistance to northern corn leaf blight and Stewart’s wilt. This sweet corn variety matures in 79 days.
Cafe is a fast-growing sweet corn that matures in just 68 days. The tender kernels are sunny yellow on ears that grow to between 7½ and 8 inches. It can handle cooler soil temperatures so it can be planted rather early. It has resistance to Stewart’s wilt and rust.
Calico is an heirloom flint corn with yellow, brown, white, purple, red and blue kernels on 6-inch ears. It can be grown as ornamental corn or for popping. It matures in 90 to 105 days.
Dakota Black is an open-pollinated popcorn that has pointed dark red kernels that are nearly black. The ears grow to be 5 to 7 inches and can be used as ornamental corn or for popping. The plants are 4 to 6 feet tall and the crop matures in 95 days.
Jerry Petersen Blue is an open-pollinated flour corn variety that makes blue corn flour. The ears are 7 to 8 inches long when ready to harvest and can also be used for ornamental corn. The plants are 7 feet tall. This variety matures in 105 days.
Glass Gem is an open-pollinated flint corn that produces three or four ears per 6-to-7-foot plant. The ears grow to be 3 to 8 inches long with kernels in an array of colors and patterns. This variety has great ornamental value and is also used for cornmeal and popcorn. It matures in 110 to 120 days.
My Fair Lady is a sweet corn meant for organic growing practices. The ears are bicolor (white and yellow kernels) and grow to be 7 or 8 inches long. The plants grow only 5 feet in height but are high yielding. This variety matures in 78 days.
Solstice is an early bicolor sweet corn variety with vigorous seedlings that mature in just 68 days. The plants grow 6 feet tall and the ears are 7 ½ inches when ready to harvest. Solstice has resistance to northern corn leaf blight.
Sugar Buns is a sugar-enhanced sweet corn with creamy yellow kernels on 7½-inch ears. The plants grow to be 5 to 6 feet tall. Sugar Buns has resistance to northern corn leaf blight and Stewart’s wilt and matures in 70 to 80 days.
Water-stressed corn plants will produce ears with missing kernels, so it’s very important to stay on top of watering a corn crop. One inch of water per week is all that’s needed, including rainfall and supplemental watering. Whenever it rains less than an inch in a week, make up the difference with soaker hoses or a drip irrigation system. Avoid overhead watering, which can promote disease and also disrupts the pollen on the corn stalks.
If you stick your finger 2 inches into the soil and it comes out dry, it’s past time to apply water. If you find that the garden is drying out quickly and/or corn plants are wilting during the hottest days of summer, step up your watering schedule to apply 1 and a half inches per week.
Corn is a heavy feeder that needs a lot of nitrogen. Prior to planting, amend the soil with compost, well-rotted manure and/or a “green manure” such as clover or vetch. This will get your crop off to a good start.
Side dress with organic fertilizer that is rich in nitrogen such as blood meal, feather meal, chicken manure, alfalfa meal or cottonseed meal when corn stalks are 10 inches tall. Apply again when the corn begins to tassel.
Corn Pests & Diseases
Corn has numerous pest and disease issues but they can be overcome by choosing resistant varieties, practicing crop rotation and employing organic controls. Installing floating row cover over seedlings can stop many insect pests from ever laying their eggs on plants. The row cover is a physical barrier that will have to be removed once the plants get a bit taller, but in the time that it is in place, it makes a big difference.
Armyworms are striped moth larvae that feed on corn foliage during cool, wet springs. Eggs and caterpillars can be removed by hand. Another option for armyworm control is Bacillus thuringiensis, known as Bt, an organic control for moth and butterfly larvae that is safe around humans and pets and will not harm other wildlife.
Common stalk borers are moth larvae. These purple and white striped caterpillars tunnel in corn stalks. Remove and destroy infested plants. They lay eggs in fall on grasses and weeds, so being a vigilant weeder is the best way to defend your corn.
Corn earworms are also moth larvae. The moths lay single eggs on corn silks, and the eggs hatch three to four days later. The caterpillars have orange or brown heads with bodies that may be yellow, pink, green or some combination of those colors. Multiple larvae may infest the same ear of corn at first, but as the larvae grow they become aggressive toward one another. Usually, just one earworm makes it to full size per ear. Corn earworms and tomato fruitworms are one and the same, and this pest attacks a variety of other crops as well. Pheromone traps can be used to alert you when these moths have found your garden. Apply Bt or mineral oil to corn silks to organically control earworms.
Corn borers are moth larvae and there are more than one species that could be present in your region, including the southwestern corn borer and the European corn borer. They tunnel into leaves, stalks and ears. Use pheromone traps to detect the moths and apply Bt to control the caterpillars.
Corn flea beetles are tiny black jumping leaf beetles, just an eighth of an inch long, that transmit Stewart’s wilt. There are chewing insects that damage corn foliage. Floating row cover can keep flea beetles from damaging vulnerable seedlings.
Corn leaf aphids are blue-green sap-sucking insects that attack the corn foliage. Their activity can also disrupt corn pollination. Aphids are small, but when their population proliferates, they can stunt or kill a corn plant. They excrete honeydew, which is a sugary substance that attracts ants and creates a black sooty mold. Keep aphids off corn with row cover and remove weeds that may also be aphid hosts plants. If you do find aphids on your plants, control them with a sharp blast of water. Once they are knocked down this way, they won’t be able to get back on the plants. Lady beetles, green lacewings and syrphid flies are all beneficial insects that prey on aphids. Refrain from using pesticides that will kill these beneficial predators.
Corn rootworms are cream-colored beetle larvae that are ⅜ of an inch long with three pairs of legs. The eggs overwinter in soil before the rootworms hatch in June or July and attack corn roots and root nodes. The adult beetles will attack the silks. They can be picked off by hand. Practice crop rotation to prevent this pest from building up its population in the soil.
Cutworms feed on roots and stems of young corn plants. The larvae overwinter as eggs or larvae, so row cover won’t resolve a cutworm issue. If cutworms are a known problem in your garden, turn up the first couple of inches of soil two weeks before planting time to expose the larvae to birds, which will reduce the number of overwintering pests significantly. Paper collars placed around each corn plant and pressed into the soil at planting time can keep cutworms at bay.
Flea beetles are chewing insects. They are tiny black or bronze jumping leaf beetles, just an 8th of an inch long. Floating row cover can keep flea beetles at bay. Another strategy is to plant a trap crop of radishes, which flea beetles prefer over turnips.
Japanese beetles are a problem for corn because they cut the silks, which prevents pollination. An adult Japanese beetle is about 3/8th of an inch long. Its wing covers appear metallic — like copper with green fluorescence — while its abdomen has five tufts of white hair on each side. A Japanese beetle larva is a white grub that grows to an inch long. Grubs are found in the soil in a curled position. Grubs can be controlled with Bacillus thuringiensis galleriae (Btg), milky spore and parasitic nematodes, and adults can be organically controlled with Btg and by hand picking. For complete information, read my guide to Japanese Beetle Prevention & Control.
Seedcorn maggots are fly larvae that are white, legless and a quarter-inch long. They feed on seeds and are mostly a problem in cool, wet weather and in gardens where manure has been applied. Seedcorn maggots overwinter as pupae in the soil. Turning the soil two weeks before planting time will expose the larvae to birds and other predators. Practice crop rotation to prevent their populations from building up.
Slugs can defoliate and kill corn plants. For a severe infestation, a bait like Sluggo, which contains iron phosphate, is a safe, organic option.
Wireworms are click beetle larvae that can spend between one and six years in soil before they emerge as adults. They are between a half-inch and 3 inches long and can kill corn seedlings and damage plants that are further along in their development. If you suspect your garden has a wireworm issue, put a potato piece 4 inches deep in the soil and mark it. After a week, dig up the potato and inspect it for wireworms. You can’t do anything about wireworms as corn is growing, but in the weeks prior to planting time, you can turn the soil several times to expose the wireworms to birds.
Corn plants can be affected by various plant diseases, including Anthracnose, rust, crazy top (Sclerophthora macrospora), leaf spot, leaf blight, maize dwarf mosaic virus and Stewart’s wilt. Aside from keeping pathogen-transmitting pests off seedlings, the best prevention for plant diseases is crop rotation. If you plant corn in the same spot for several years, corn pathogens will build up in the soil. Instead, wait four years before planting corn in the same spot again.
Corn typically produces one to two ears per stalk, though there are higher-yielding varieties to be found.
For sweet corn, the ears are ready to harvest when the silks turn from light yellow to dark brown. Wait to harvest flint corn until just before the first fall frost. Popcorn and flour corn should be harvested when the kernels are hard and glossy.
Pick sweet corn early in the morning, when the kernels will be at the highest moisture levels. To harvest any type of corn, grasp the ear, twist and pull downward.
Keep sweet corn in their husks until ready to cook. If roasting the corn, the husks can actually stay on while the corn cooks. Eat the kernels right off the cob or remove the kernels from fresh or roasted corn with a sharp knife. Uncooked kernels can also be frozen or canned.
Store flint corn, flour corn and popcorn in a dry place. Peel back the husk and hang the ears to allow the kernels to dry out further.
What are your secrets to growing corn successfully? Let us know in the comments below.
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Links & Resources
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joegardener Online Gardening Academy™: Three popular courses on gardening fundamentals; managing pests, diseases & weeds; and seed starting!
joegardener Online Gardening Academy Beginning Gardener Fundamentals: Essential principles to know to create a thriving garden.
joegardener Online Gardening Academy Perfect Soil Recipe Master Class: Learn how to create the perfect soil environment for thriving plants.
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