Planting, Growing, and Harvesting Sweet Corn
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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.
How to Plant Corn
- To speed germination, moisten seeds, wrap in moist paper towels, and store 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.
Check out this video for great tips on growing juicy corn:
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:
- ‘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!
Gardening Products
- 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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I really appreciate this article on corn and have a question. This is our first year having grown popping corn which was going really great till some very adorable squirrels got into it and after trying a bunch of different ways to keeps them out of the corn we finally decided to pull the fully ready ones (not dried) and are hoping it’s possible to dry them inside but is it possible? The rest we left with cages over the ears of corn. Not mad at the squirrels bc it’s just nature but hoping we will still be able to have something to show for it. Thank you in advance
Dear Ello,
Thank you for your note about your furry wild popcorn-loving neighbors. Yes, if the corn is ripe, you can dry the ears inside. Here is our guide to growing popcorn including advice for harvesting and drying. Good luck and happy popping!
—The Editors
This is my first year growing corn in my backyard garden.
Trying to find out what to do after harvest has been quite difficult/information is unclear.
Do we leave the stalks in the ground for a while after harvest? Remove entirely/to a certain height?
Thanks,
Ontario, Canada 🇨🇦
You will want to remove the stalks soon after harvest. There are a number of pests that will use what remains after harvest as a winter home and by removing the stalks you will greatly reduce their chances of survival. But you have a few options of what to do with your stalks.
You can cut them down and put them in your compost pile. We suggest cutting them up some to increase the rate of decomposition. You will then want to till the stalk nubs back into the soil. You can also till all of it into the soil. There are a lot of great nutrients that remain in corn stalks and it will provide good organic matter for next year’s plantings once it breaks down.
And if you want to think ahead, cut some of the stalks and dry them upside down and they will make for great decor when fall rolls around!
Could you please post how you boil corn and how you barbeque it. How long should you boil it for or leave it on the barbeque. Thank you
Hi, Louise. When you boil corn on the cob, allow the water to come to a full boil and then add in the ears of corn. Cook it for 5 minutes. When it comes to cooking corn on the cob on the grill there are several methods. Try this: peel the corn and remove the silk. Pull the husks back up and then soak the ears in salted water for about 10 minutes. Remove and make sure to shake off any excess water. Place the ears on the grill, close the lid, and turn every 6 minutes. Your corn should be ready after 20 minutes.
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.
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