Garden Variety: Tips for growing sweet corn and popcorn

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Sweet corn and popcorn are popular vegetable garden crops with a rich history of cultivation in North America. They are closely related to each other, to flint corn and flower corn, to the starchy field corn produced in large fields across the country, and to maize produced by Native Americans thousands of years ago.

Despite the rich history of corn and its popularity in home gardens, sweet corn and popcorn are challenging crops for many gardeners. Successfully producing succulent ears of sugary sweet kernels or large starchy kernels that explode into flavorful popcorn requires attention to planting and pollination needs, adequate water and nutrients, protection from wildlife and knowledge of crop pests.

Planting and pollination requirements must be considered together. Pollination is necessary for kernel production and only occurs when pollen from the tassels at the top of the plants reaches the silks along the stalk. Wind aids the movement of pollen to the silks. A single corn plant can pollinate itself, but pollination is more effective when corn is planted in blocks and pollen can fall to silks of multiple corn plants all around. Cultivation guides might say to plant several short rows rather than in one or two long rows. Another way to think about it is to make a square or rectangle that is at least four to six rows wide.

Although pollination is better when corn is planted in blocks, flavor and uniformity are best when a singular variety is involved. This is called isolation.

Pollination isolation is achieved by growing one variety of corn in the garden, planting multiple varieties of corn that flower at different times, or planting multiple varieties of corn at different times and ensuring that flowering of each variety occurs at a different time.

Use the “days to maturity” description on the seed packet to determine planting schedules and avoid cross-pollination of multiple varieties.

Sweet corn and popcorn growing near plots of field corn (also called dent corn) may cross-pollinate with that corn. Unless you know the field corn flowering time, plant sweet corn and popcorn at least 300 feet from field corn plots to avoid cross-pollination.

Soil temperature is the next consideration. Use a soil thermometer or other thermometer with a long probe to check soil temperature prior to planting. Plant corn when temperatures are consistently 60 to 65 degrees or above. Planting in cold soil may result in rotten seed or plant diseases in new seedlings.

If possible, test soil nutrient levels prior to planting and follow recommendations to improve fertility prior to planting if needed. Corn grows best when adequate nitrogen is present. Most crops benefit from additions of nitrogen fertilizer when plants are about a foot tall.

Corn requires adequate water to maximize production. Plan to provide supplemental water to corn crops during extended dry periods.

Wildlife are the most destructive pests of corn in northeast Kansas. Raccoons are the hardest to control, with deer as a close second. Coyotes will also sometimes feed on sweet corn. This is a bigger issue with sweet corn than popcorn, but animals may taste-test the popcorn ears before leaving them alone.

Electric fences or tall (8-foot for deer) nonelectric fences are the best bet to keep raccoons and other animals away from sweet corn. Use an electrified mesh fence, or for raccoons only, use a two-wire system with wires at 4 inches and 12 inches above the ground. For deer, add a third wire at 36 inches with flagging ribbons to make it visible, or use hot tape for the third strand.

Corn is also susceptible to multiple insect pests and plant diseases. Watch for signs and symptoms of pests. When and if they occur, seek out resources to identify the pest and determine the best course of action.

— Jennifer Smith works in regulatory horticulture and has worked as a horticulturist for various government entities. She has experience in landscape design and maintenance and as an educator.


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