Planting, Growing, and Harvesting Sweet Corn
Plant in full sun (at least 6 to 8 hours of direct sunlight). Corn plants are picky about their soil. It should be well-draining yet consistently moist, as corn tends to suck up a lot of water. Ideally, aged manure or compost should be worked into the soil in the fall. If that’s not possible to do, simply mix in aged compost prior to planting.
When to Plant Corn
- Starting corn indoors is not generally recommended. It’s best to start them directly in the garden 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. It’s vital to plant early, since corn requires a long growing period of frost-free weather. See average frost dates and our Planting Calendar for corn based on frost dates (keep in mind these dates are average or typical and simply a guide).
- If you live in an area with a shorter growing season, choose an early variety that will mature well before the first fall frost
- Also, in colder zones, 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.
How to Plant Corn
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To speed germination, moisten seeds, wrap in moist paper towels, and store in a plastic bag for 24 hours.
- Sow seeds about 1½ to 2 inches deep and 2 to 4 inches apart in short, side-by-side rows to form a block, rather than one long row.
- For decent pollination, we recommend a modest block of, say, 10 to 50 plants.
- You may choose to fertilize at planting time with a 10-10-10 fertilizer; corn is meant to grow rapidly. If you are confident that the soil is adequate, this step can be skipped.
- Water well at planting time.
Check out this video for great tips on growing juicy corn:
Types of Sweet Corn
Hybrid corn varieties are divided into four main categories based on their sugar content and genetics: sugary (su), sugar-enhanced (se), shrunken (sh, sh2), and synergistic (sy). These categories are namely used to indicate a variety’s sweetness and are usually 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:
- ‘Argent’: sugar-enhanced variety, good taste. White kernels.
- ‘Iochief’: 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. Check out our video to learn more about growing and using painted mountain corn.
- 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.
- Sugary (su) varieties begin to lose their sweetness soon after harvesting, so use them as soon as possible.
- Prepare for eating or preserving immediately after picking.
- 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.
How to Store Corn
- Sweet corn freezes well, especially if removed from ears before freezing. Learn how to properly freeze corn.
- Corn can also be harvested for other purposes!
- 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.
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All in the article is well and good...BUT what about the GMO corn that does not have a natural taste ?? The artificial over sweer sugar taste that makes some of us nausiated after 2 bites as opposed to heirloom corn. All of the corn at the supermarket and many farm produce stands is GMO corn and the GMO corn is un natural and has a strange taste
When starting any plants off from seed why not use cardboard or paper containers such as paper cups (you can buy 50 or more new cups for only a few dollars). Place a few holes into the base of the cup or cardboard container for drainage. The container with the single seedling can then be planted directly into the ground without disturbing the roots. The cardboard or paper container will decompose into the soil adding nutrients back into the soil. You can clearly mark each cup or container directly onto the side with any information you need, Date, variety etc. Happy planting.
Thanks for the excellent growing tips for corn. I live in zone 7a and was surprised to see the planting times. I realize it's a guide but would stress to others that average soil temps should determine actual planting dates. I rarely plant corn before mid may. Last year with the sugar enhanced variety it was May 28th, which according to my log is the latest planting in 30 years of growing corn.
Starting earlier when the soil is cooler than optimal has no advantage and may have the opposite effect when the weather is cool and wetter than normal. Thanks again.
The basic information provided on sweet corn its verities and farming is enlightened indeed.
Thank you from Solomon Islands South Pacific Ocean.
My corn has extra large kernels. Wondering why?
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