Growing Popcorn

Popcorn (Zea mays var. everta) is a member of the grass family and, other than sweet sorghum, is the only member of that family that is intentionally grown in the garden.

There are many types of corn, including popcorn, sweet corn, dent corn, pod corn, flour corn and flint corn. Popcorn is distinguished from other corns by its explosive seed when exposed to high temperatures. It has been cultivated for several thousand years. There are two types of popcorn grown, pearl and rice. Pearl popcorn has round smooth kernels, while rice popcorn kernels are elongated. Varieties can be grown for red, pink, blue, yellow and multicolored ears. The plants can be shorter than sweet corn. Even though the yield is about the same, popcorn lasts much longer in storage. The quality of popcorn depends on the conditions during growing, harvest and storage.

Growing Popcorn

Popcorn needs full sun and rich, well-drained soil. Plant popcorn when all danger of frost has passed and the soil is warm. Sow seed directly in the garden in spring. Sow the seeds 1 to 2 inches deep (about two seeds per hole) and space them 8 to 10 inches apart, watering thoroughly. Thin germinated seeds later, if needed. Grow popcorn plants in several short rows spaced 18 to 24 inches apart to ensure good pollination and well-filled ears.

Do not plant sweet corn and popcorn in the same garden; if they happen to shed pollen at the same time, the sweet corn quality might be reduced.

Choose a location with access to irrigation because, just like other corn plants, popcorn plants require plenty of water during the growing season. Drought stress seriously impacts the quality of the harvest, so keep the soil moist at all times. Popcorn needs 1 1/2 to 2 inches of water per week from either rain or irrigation.

Popcorn needs an abundance of nitrogen during the growing season. When the plants are about 6 inches high, side dress with 1/2 pound of high-nitrogen fertilizer per 100 square feet. Spread the fertilizer down the sides of the rows and water it in. Side dress again with 1/4 pound of fertilizer when plants are about knee high or once the ears form silk.

Weeds compete with popcorn for nutrients and moisture. Cultivate the soil around the plants regularly to eliminate weeds. Take care not to damage the roots or pull the soil away from the plants while cultivating.

Water, fertilize and weed regularly. When the corn is about knee high, add soil over the exposed roots for good support. Any serious stress can greatly reduce yields and the quality of the popcorn.

If growing popcorn late in the season, determine how many days until maturity (usually this information is on the seed package) and make sure it will have time to mature before frost.

Pollination Considerations for Popcorn

Popcorn is wind pollinated. Growers can manually help pollination by gently shaking the stalks. The pollen of the male flowers (the tassels) need to reach the female flowers (the silks). Planting in squares will drastically improve pollination as the wind-blown pollen grains will have a better chance at landing on another corn stalk. Sixteen stalks in a 4-foot by 8-foot area is a minimum for good pollination.

The wind pollination can be an issue if growing two types of popcorn, especially if planning to save seed. You could get cross-pollination. Separate planting dates by a couple of weeks so that the corn doesn’t tassel at the same time, or grow the same type of popcorn.

Popcorn Cultivars

Several different varieties are available to home gardeners. Be sure to select a variety that will mature in your area.

Most seed catalogs list popcorn varieties for home gardeners. To find one that grows best under conditions in your area, try several over a couple of years; and keep testing new ones as they come on the market. Maturity is important in variety selection because popcorn that does not reach full maturity before frost will have very poor quality.

Tom Thumb popcorn grows to be about 3 feet tall and is a popular cultivar (variety) all over the country.

Disease Concerns for Popcorn

Stalk and root rot diseases are often the most destructive in popcorn. Symptoms are usually first noted when the crop nears maturity. Diseases are generally caused by several fungal and/or bacterial pathogens rather than a single causal agent. Yield losses result from infected plants through poorly filled ears or lodged plants.

Control of popcorn diseases involves a combination of sound growing practices, which include crop rotation, proper fertilization, proper management of crop residue, use of disease-resistant hybrids and possibly appropriate applications of chemical treatments.

Harvest of Popcorn

Popcorn matures 100 days or so after planting. Each ear yields one serving of popcorn, and each plant produces one or two ears.

Allow the kernels to dry in the field as long as possible. When harvested, the kernels should be hard and the husks completely dry.

Let the popcorn ears remain on the stalks until the husks are dry. Harvest the ears when the husks are brown and the kernels are hard and shiny. The downside here is this takes time that could be used to start another crop. Bring it inside to finish drying for several weeks. You can remove the corn kernels from the ears by hand, by twisting the kernels off or by rubbing two cobs together. It is fairly easy to remove the kernels by flicking them off with a thumb.

After harvest, remove the husks and place the ears in mesh bags and hang in a warm, dry, well-ventilated location. The ideal moisture content for popcorn is between 13 and 14 percent. Once or twice a week, shell a few kernels and try popping them. When the test kernels are popping well and tasting good, shell and store the rest of the kernels. If the popcorn is chewy or the popped kernels are jagged, it is too wet and needs to continue drying.

Popcorn Storage

The chaff can be removed by pouring the kernels from one container to another outdoors, allowing the wind to remove the debris. After the popcorn has been cleaned, store the kernels in airtight containers. If stored properly, popcorn should retain its popping quality for several years. Unshelled corn should be stored at temperatures near 32 degrees Fahrenheit and high relative humidity. The storage location should also be rodent-proof.

If stored popcorn fails to pop, it may be too dry. Add one tablespoon of water to a quart of popcorn. Cover and shake at frequent intervals until the popcorn has absorbed the water. After three or four days, test pop a few kernels to see if it is ready. Add more water and repeat the process until the popcorn pops well.

Popcorn Nutrition & Cooking Considerations

Popcorn is a whole-grain food and a great source of vitamins, minerals and antioxidants. Popcorn contains a high level of polyphenols, a type of antioxidant proven to help prevent cancer. 

Americans consume 16 billion quarts of popped popcorn a year. This snack food is an important and potentially healthy part of U.S. diets when additions of butter and salt are reduced.

Author: Brandy Brabham, WVU Roane County Extension Agent – Agriculture and Natural Resources

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