The process of saving corn seeds allows gardeners to preserve preferred varieties and develop strains adapted to their specific microclimate. For predictable results, it is important to begin with open-pollinated or heirloom corn varieties, not modern hybrids. Hybrid corn is a first-generation cross whose seeds will not produce plants true to the parent type, resulting in unpredictable traits and reduced vigor. Open-pollinated corn produces seeds that consistently grow into plants resembling the parent, ensuring desired characteristics are maintained.
Selecting and Isolating Parent Plants
Successfully saving corn seed depends on managing cross-pollination, as corn is a wind-pollinated plant with separate male and female flowers on each stalk. The male tassel releases pollen that can travel significant distances to fertilize the silks on another plant. To maintain seed line purity, plant only one corn variety for seed that season, or ensure significant isolation distance. Home gardeners often need a minimum separation of 600 feet from other corn varieties to prevent pollen drift.
When planting multiple varieties in a smaller area, controlled pollination techniques must be used. One common method is detasseling, which removes the pollen-producing tassels from the seed-bearing plants (“female” plants) before they shed pollen. This forces the female plants to be pollinated only by a designated “male” block or by hand-pollination.
Hand-pollination involves covering the tassel with a paper bag to collect pollen, and covering the silks on the ear with a small bag before they emerge. Once collected, the pollen is dusted onto the exposed silks of the same plant or another selected female plant. The ear is immediately re-covered to prevent contamination from outside pollen.
Select parent plants for seed saving based on superior traits, such as vigorous growth, disease resistance, and desirable ear characteristics. It is important to save seed from at least 50 to 100 plants to maintain genetic diversity and prevent inbreeding depression, which can reduce the variety’s long-term health and yield.
Harvesting and Curing the Ears
Recognizing the correct stage of maturity is important for harvesting corn intended for seed. Corn kernels reach physiological maturity at the “black layer” stage, where a dark layer forms at the base of the kernel, indicating maximum dry weight. At this point, the kernel moisture content is typically around 30 to 35%, and the plant is safe from frost damage.
The husks will have turned brown and dried completely on the stalk, indicating the ear is ready for seed harvesting. Unlike corn grown for eating, seed corn must be left in the field past the edible stage to dry down naturally. Ears selected for seed should be twisted off the stalk and the husks pulled back to expose the kernels to air, which hastens the drying process.
Initial curing involves drying the harvested ears while the kernels are still attached to the cob. The ears should be placed in a cool, well-ventilated area, often braided or hung in mesh bags to allow for air circulation. This initial, slow drying phase helps reduce the moisture content gradually and prevents the growth of mold or mildew, which can destroy the seed’s viability. This on-cob drying should continue for several weeks until the kernels feel hard and dry to the touch.
Preparing Seeds for Long-Term Viability
After the initial curing period, the corn must be shelled. This is typically done by hand or with a hand-sheller once the kernels are hard enough to resist denting. The goal of this final preparation is to reduce the seed’s moisture content to a safe level for long-term preservation, ideally between 10 and 12%.
This low moisture level minimizes the metabolic rate of the seed embryo, slowing the natural decline of viability. A simple way to check for sufficient dryness is the hammer test: striking a few kernels with a hammer on a hard surface. If the kernels shatter cleanly rather than flattening or crushing, they are likely dry enough for storage. If they are still soft, they require further drying in a warm, dry area with good air movement.
Storing Seeds for Next Season
Once the kernels are shelled and fully dried, they should be placed into airtight containers to prevent them from reabsorbing moisture. Suitable containers include glass jars with tight-fitting lids or sealed moisture-proof bags. The storage environment should be consistently cool, dark, and dry to maximize seed longevity.
The ideal storage conditions follow the principle that the sum of the storage temperature in degrees Fahrenheit and the percentage of relative humidity should be less than 100. For example, 50°F combined with 50% humidity is considered excellent for maintaining viability. For extended storage periods beyond a single season, refrigeration between 35°F and 40°F, with the seed in sealed containers, is often recommended.