Sweet Corn

Grow your own sweet corn this summer!

November 26, 2010

I grew up in the Midwestern Corn Belt, where one of summer's enduring memories is stopping at farmers' stands along rural highways to buy fresh sweet corn picked in the morning and eating it that evening. But as a gardener, you can eat corn that's even fresher- you can start the cooking water boiling before you've even harvested the ears and allowed any of the luscious sugars a chance to turn into starch. Think you need a farmer's size field to grow your own sweet corn? With a few time-tested techniques, you can use your garden space efficiently to grow a few meals of this classic American crop in any size plot.

Sweet, Sweeter, Sweetest
Sweet corn can be divided into three major groups: standard, or normal sugary (su); sugar-enhanced (se); and supersweet, or shrunken (sh2). Standard sweet corn varieties offer traditional flavor, and they germinate better in cold soils than others. But their sugar turns to starch quickly after harvest. This may be why most farmers are raising the other two types, but it will be less of concern to you. Sugar-enhanced varieties are sweeter and more tender than standard, and supersweets are the sweetest of all but are less vigorous than other hybrids and need moist, warm soil to grow well. You can choose white, yellow, or bicolored varieties of all three types- the differences are strictly a matter of personal preference. If you want to grow a whole season of corn, plant early, midseason, and late varieties. Where diseases and pests are known to be a problem for gardeners, look for resistant varieties. With so many choices and factors, your best bet for narrowing down varieties is to talk to your local Cooperative Extension agent, farmers' market vendors, or other home gardeners in your area to find out which varieties perform best in your conditions. To help you get started, we've named our top picks, which perform well in a broad range of conditions.


In the Hills
Soil preparation:
Corn has fairly shallow roots, and it uses a lot of nitrogen and other soil nutrients. To help your crop get off to a strong start, prepare the soil first with a nitrogen-rich fertilizer such as chicken manure or compost (use about 20 to 30 pounds for 100 square feet).

Site. Plant in the southwest side of the garden so the tall corn plants won't shade out the rest of your crops (or grow corn where it will shade greens and other plants that cannot tolerate direct summer sun).

No rows. Corn is wind-pollinated, so a square plot is more effective than long rows and it can help you use limited space efficiently. The Zuni Native Americans of the Southwest plant corn in hills in a square. Sow four to five seeds in hills, leaving 3 to 4 feet between each hill and making a square, advises George Dickerson, an extension horticulture specialist at New Mexico State University. Thin the seedlings to three or four in each hill by cutting the extra seedlings at ground level. Even in a small plot, the square formation ensures pollination no matter which direction the wind blows.

Timing. Corn germinates best in soil that's warmer than 60°F. Corn seed sown in cold, moist soil is susceptible to fungal disease, says Rosie Lerner, extension specialist at Purdue University. "When in doubt, wait," she advises. If you have a short growing season or just want to get your corn off to a quick start, try pregerminating seeds indoors in biodegradable pots (corn doesn't transplant well). Or warm the soil by covering it with clear or black plastic for a week or more so the sun can raise its temperature.

Succession. If you want a few harvests of corn, plant early, midseason, and late varieties in early summer, or plant your favorite variety every 2 weeks for 6 weeks. Beware of cross-pollination of different varieties, which can result in tough, starchy kernels. Be particularly careful to isolate the supersweet varieties by time (timing your plantings so that the supersweets are not shedding pollen at the same time as other varieties) or space (200 to 400 yards between varieties).

Saving space. Plant corn together with pole beans and vine crops like cucumbers, squash, and pumpkins, suggests Pete Ferretti, professor of vegetable crops extension at Penn State University. "Pole beans and vine crops planted on the sunny side of a row of corn will grow up the stalks, which doesn't hurt the corn."

Corn Care
After planting, keeping your corn watered is your most important concern, especially during pollination. If corn suffers a drought then, you'll end up with only a few kernels on each cob. Use drip irrigation or a soaker hose to get the water right to the corn's roots. An inch or two of mulch (straw or grass clippings work well) between the stalks helps keep the soil moist. If you grow squash amidst the corn hills, its leaves will act as a living mulch, but it will also compete with the corn for moisture, so soak the soil well when you water. Sidedress the stalks with a nitrogen-rich fertilizer a month after planting your corn, then again when tassels appear. Perhaps the most important favor you can do for your corn is to hand-pollinate to ensure that each ear fills out completely. Lerner simply grabs the tassels and shakes them to distribute the pollen to the silks below. A more time-intensive method is to gently shake the tassels into a small paper bag, collecting the pollen, then sprinkle the pollen onto the emerging silks, repeating once or twice over the next few days.

Problem Solving
Birds (especially crows), insects, and raccoons seem to love corn as much as we do. The most widespread pests are European corn borers and corn earworms. You can outwit the former by planting a week or two after the soil warms and avoiding the borers' emergence. The best way to foil corn earworms is to choose a variety that is resistant to this pest because it has a tight husk. If you notice corn earworm during the season, help prevent infestation by applying a small amount of a 20-to-1 mix of BT (Bacillus thuringiensis) and mineral oil to the silk at the ear tip just as the silk begins to wilt. (You can get a special tool for applying this treatment, Zea-Later II, for $79 from johnnyseeds.com.) If larger critters like birds and raccoons are getting to your corn, try wrapping duct tape around the ear an inch above the stalk and an inch below the tip. (See, duct tape really is a cure-all.)

Picking and Eating
Though seed packets list maturation dates for each variety, the timing for when corn has reached its peak varies according to your specific conditions and what the climate has been like during the growing season. Check yours when the silks are brown and damp by poking a fingernail into a kernel-it's ready when the liquid that squirts out is milky. Sweet corn has a window of just a few days at its peak before the sugars start turning to starch, so if it's not possible to pick it all within that time frame, use older, starchier ears in cooked dishes like stews and chowders. After all, nothing says summer like the sweet pleasure of starting a pot of water on the stove, racing out to the garden to pick a handful of ears, and eating it just a few short minutes later. Gretchen Roberts, a food and gardening writer in Fort Wayne, Indiana, can just about taste this summer's first ear of corn right now.

How Many Ears? A reliable rule is to sow three seeds for each plant you want to grow, and to thin to the strongest seedling, since corn's germination rate is around 75 percent. Plant about 15 plants per person for fresh sweet corn, plus 30 or more plants per person for freezing and canning.

6 Fresh Ideas for Corn Everyone knows sweet corn tastes best cooked right from the garden and slathered with butter. But if you're blessed with an abundant harvest, try some of these fresh ways of enjoying corn.

Zap it. To remove the silks as easily as peeling a banana, husk just the outer leaves and trim the silk tips. Wrap the corn in a damp paper towel, microwave for a minute or to taste, and then shuck the corn. The silks should slide right off.
Spice it up. Cut cooked corn off the cob and toss it with chopped chile peppers, tomatoes, cilantro, lime juice, and garlic for a fresh salsa.
Grill it. Trim off the top silks and grill the corn, still in its husks, over medium-high heat for 15 minutes, turning frequently. Use hot pads when peeling the husks, and serve the corn with sour cream sprinkled with cayenne pepper, which you can spread like butter on the cob.
Sauce it. Puree cooked corn with avocado and seasonings for a nutritious, pretty green-gold pasta sauce.
Soup it up. Simmer a sweet corn chowder and top with crème fraîche. Sweeten the pot. Make a sweet corn custard by cooking pureed sweet corn with milk, sugar, and eggs.

The Cream of the Crop

Early: 'Fleet', 'Sugar Buns', 'Trinity

Midseason: 'Bodacious', 'Luscious', 'Tuxedo'

Late: 'Country Gentleman', 'How Sweet It Is', 'Silver Queen'


1. High Mowing Seeds,Wolcott, VT; 802-472-6174, highmowingseeds.com
2. Baker Creek Heirloom Seeds, Mansfield, MO; 417-924-8917, rareseeds.com
3. Fedco Seeds, Waterville, ME; 207-873-7333, fedcoseeds.com
4. Johnny's Selected Seeds, Winslow, ME; 800-879-2258, johnnyseeds.com
5. Park's Gardens, Greenwood, SC; 800-213-0076, parkseed.com