Planting, Growing, and Harvesting Sweet Corn
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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.
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:
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.
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.
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!
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.
Catherine Boeckmann
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I'm going to plant a 2 by 6 foot block. I'm going to grow peas around the stalks and zucchini at the base. Does this make sense? Do you have any recommendations or tips?
Grow each crop in separate areas. Over cropping will deplete the soil nutrients. Tall plants will shade the smaller plants and stunt them. Plants need sunlight.
I have a big potato patch on the north side my garden, about 10'x10'. Can I plant corn in this patch in between my potato rows, or does corn need more space? I've tried growing corn three summers now, and never get good results. I don't want to devote so much space to a crop that might not grow, so I want to plant it where I've already got something going (in case its another failed experiment). But will it hurt my potatoes?
Each crop needs it's own space. Tall plants will shade smaller plants and they will suffer. Corn needs to be planted about 8" apart in rows about 2-2.5' apart. 2-3-4 rows. Pollen falls from the tassel down to the ears of corn - usually for about 5 days and mid morning generally. IF YOU have strong winds while this happens you will have pour pollination. When the plants are pollinating, go out in the morning and run your hand up the tassel and then rub the ear silks. Do some research about growing it - it is pretty simple to grow - right spacing. good fertilised soil and plenty of water. And get the pollination right.
As far as companion plants, corn and potatoes do fine, although corn is a heavy feeder, while potatoes are medium feeders and do better without as much nitrogen (which encourages foliage rather than tuber formation). However, the other thing to keep in mind is the height of the corn. Plant them on the north side of the garden, so that they don’t shade the shorter potato plants too much. Also, corn, which is wind pollinated, does nicely in the garden when planted in blocks rather than rows.
Hey, So I am a first time gardener. I have put some sweetcorn into my garden that I have built an enclosed mesh protective cage over to keep unwanted preditors out. The issue I have is that the sweetcorn has grown taller than I expected and is pushing through it. What would happen if I were top the stalks. Is there anything else that I could do to save the corn.
Cheers Willie
I would have put posts in the corners and sides if needed to lift the mesh up to 6-7' high. The cobs should be high enough that thinks can't eat them.
Welcome to gardening, Willie! We have seen folks in a small-plot community garden create a mesh cage for the corn, specifically to keep critters away. We can not recall how that grower may have handled his tallest stalks. Check the seed packet/source to see how tall the corn can be expected to get. If it is not a whole lot taller, perhaps you can add a sort of mesh cover to the arrangement. If it is a lot taller,you might want to remake the cage to make it higher. It would seem a shame to put the crop at risk. Maybe you can use the existing cage, separately, as a pea fence or cuke/squash/melon vine trellis. Don’t think of the effort as wasted; there is always another use for the mesh.
In the meantime, we looked into the idea of topping off. Apparently, farmers who grow corn for seed corn production top off (cut off) as much as two feet of the stalk. This removes the tassels so that the plants can only be pollinated by other plants. This goes on to say that the rows of corn that are topped are female; the rows that are not topped are male. Pollen is produced on the tassel and crossbreeding begins. The result is hybrid seed. You probably do not want to do that.
We wish you the best—
There is no such thing as male and female corn plants. It is the pollen from the tassel that fertilises the silks on the ear. Each silk will produce a kernel on the cob.
My corn is about 2 feet high and I wonder if I should remove the shoots that appear on the stem near the ground or leave them on
Thanks
