The common pantry staple used for a movie night snack is the mature seed of a specific corn variety. Corn, scientifically known as Zea mays, is botanically a grain, and all corn kernels contain an embryo that can germinate. While the answer to whether they can grow is technically yes, the success rate of planting grocery store popcorn kernels is often low. This low success rate is due to commercial processing and the kernels’ genetics.
Popcorn Versus Other Corn Types
Popcorn, classified as Zea mays everta, is a distinct subgroup of corn that differs genetically and structurally from other types. The corn plant has six primary varieties, including sweet corn, dent corn, flint corn, flour corn, pod corn, and popcorn. Popcorn is technically a type of flint corn, characterized by a hard, nearly impermeable outer shell, or pericarp, surrounding a dense, starchy endosperm.
This unique structure, combined with a precise amount of moisture sealed inside the kernel, allows it to pop. When heated, the internal moisture turns to steam, building pressure until the kernel explodes, turning the dense starch into a foam. Sweet corn, which is eaten off the cob, has a high sugar content and a soft, thin pericarp, making it unsuitable for popping. Dent corn, or field corn, is used for animal feed and industrial products, and its soft starch structure also prevents popping.
Are Store-Bought Kernels Viable Seeds
The journey from the farm to the grocery store significantly compromises the viability of popcorn kernels intended for planting. Most commercial popcorn is dried to an optimal moisture content of 13.5% to 14.5% for popping. This moisture level is lower than what is required for successful germination. Some commercial kernels may also be treated with heat or mild irradiation to prevent pests or mold, processes that can destroy the seed’s embryo.
A major obstacle for home growers is the genetic makeup of the kernels, as nearly all commercial popcorn is an F1 hybrid variety. Hybrid seeds are created by crossing two parent strains to achieve desirable traits like high yield or disease resistance. While the kernels from the bag will grow, the resulting plants (the F2 generation) will not “grow true” to the parent. These plants may produce small, low-quality ears with poor popping performance. For a reliable popcorn harvest, gardeners should purchase open-pollinated or heirloom seeds, which produce plants identical to the parent generation.
How to Plant and Grow Popcorn
For those attempting to grow store-bought kernels or using purchased viable seeds, testing for germination beforehand is recommended. The wet paper towel method involves placing a small sample of kernels in a damp paper towel inside a sealed plastic bag and keeping it warm for several days to see how many sprout. Popcorn is a warm-season crop, requiring direct sowing after all danger of frost has passed and the soil temperature consistently reaches 60°F or higher.
The corn plant is a heavy feeder, requiring rich, well-drained soil and consistent watering, especially during the tasseling and silking stages. Proper spacing is important for successful pollination, which is achieved by wind, not insects. Seeds should be planted about one inch deep, spaced 8 to 10 inches apart. Plant the seeds in blocks of short, multiple rows rather than a single long row. This block planting ensures that pollen from the male flowers (tassels) has a higher chance of reaching the female flowers (silks) on neighboring plants, leading to fully developed ears.
Harvesting and Curing the Kernels
Harvesting popcorn requires patience, as the kernels must dry on the stalk far longer than sweet corn. The ears should remain on the plant until the husks are completely dry, papery, and brown, and the kernels are hard and glossy. This usually occurs late in the season, approximately 90 to 120 days after planting, depending on the variety. Waiting until the entire stalk is brown and dead is the best indicator that the kernels are mature.
After harvesting the ears, they must be shucked and cured further in a cool, dry, and well-ventilated area for several weeks. This post-harvest drying reduces the kernel’s moisture content to the ideal range of 13% to 14.5% for popping. A simple “pop test” can be performed by shelling and popping a few kernels. If they pop well and are fluffy, the corn is ready for shelling and storage in airtight containers. If the kernels fail to pop or are chewy, they require more drying time.