Corn is a unique and rewarding crop for seed saving, but its specific biology requires careful attention for successful results. Unlike many garden vegetables, the corn kernel itself is the seed, and its characteristics are immediately affected by the pollen it receives. Preserving a desirable strain, such as a treasured heirloom or a variety adapted to your local climate, is a process that begins long before harvest. Navigating the unique challenges of corn’s reproductive cycle and moisture needs is the first step toward securing a reliable seed supply.
Preventing Cross-Pollination
The first consideration for saving corn kernels is ensuring varietal purity, which is complicated by the plant’s wind-pollinated nature. Corn is monoecious, meaning each plant has separate male flowers (the tassel) and female flowers (the silks on the ear). Each strand of silk must receive pollen to develop a single kernel, and this pollen drifts freely on the wind. The seed produced will express the traits of both the mother plant and the pollen donor, a phenomenon known as xenia. Because of this, only open-pollinated (OP) corn, not hybrid (F1) corn, should be saved for seed, as F1 seed results in unpredictable offspring.
To keep a variety pure, it must be isolated from all other corn varieties, including different types like dent, flint, sweet, or popcorn, which can all cross-pollinate. Isolation can be achieved either by distance or by time. For a small garden, a spatial separation of at least 600 feet from other corn is often recommended, since most pollen falls within 20 to 50 feet of the source. Alternatively, planting varieties so their silking and tasseling periods are separated by at least two weeks can prevent them from flowering at the same time. Growing a larger block of plants, ideally 100 or more, also helps ensure that the silks are overwhelmed by pollen from the same variety.
Selecting and Harvesting Mature Seed Ears
Seed selection begins while the plants are still growing vigorously in the field. Choose plants that exhibit the most desirable characteristics, such as strong stalks, good disease resistance, and high productivity. It is important to select multiple plants to maintain the genetic diversity within the variety, which keeps the strain robust and adaptable.
The ears must be left on the stalk until they are fully mature, well past the stage for fresh consumption. Seed readiness is indicated when the husks have completely dried out and turned brown, and the kernels are hard and glossy. Harvesting should occur on a dry day before the first hard frost to minimize moisture and prevent mold development.
After harvesting, the ears chosen for seed should be peeled back to examine the kernels for uniformity and health. The kernels at the tip and butt of the ear are often poorly pollinated, smaller, or less viable than those in the middle. These end kernels should be discarded, as they can reduce the overall quality and germination rate of the saved seed lot. Only the plump, uniform kernels from the central portion of the ear should be retained for planting.
Curing and Preparing Kernels for Storage
Reducing the moisture content of the kernels after harvest is the most important factor for long-term seed viability. Corn kernels typically contain 32% to 40% moisture at maturity, which is too high for safe storage. This excess moisture must be reduced slowly through curing, a process that typically requires several weeks. The goal is to bring the kernel moisture level down to an ideal range of 10% to 12%. Higher moisture levels favor mold growth, insect activity, and rapid deterioration of the seed’s internal structures.
To cure the ears, pull back the husks to expose the kernels fully, then braid or tie the ears together in bunches. Hang these ears in a cool, dry, and well-ventilated area, such as an open shed or attic, protected from rodents and weather. Adequate airflow is essential to carry away the moisture released by the drying kernels. Shelling the kernels should only happen once they are thoroughly dry and hard, as attempting to shell them too early can damage the embryo and reduce germination.
Long-Term Storage and Testing Viability
Once the kernels are properly cured and shelled, they must be placed in conditions that preserve the low moisture content. Ideal long-term storage involves a cool, dark, and dry environment with a consistent temperature, as heat and humidity accelerate the natural breakdown of viability. A common guideline suggests that the sum of the storage temperature (in degrees Fahrenheit) and the relative humidity should be less than 100. Airtight containers, such as glass jars or heavy-duty freezer bags, are suitable for protecting the kernels from moisture fluctuations and pests.
Place the dried kernels in these containers and store them in a location like a refrigerator or a cool basement. For very long-term storage (over a year), a moisture content of 10% or less is recommended to prevent quality loss. Before the next planting season, perform a simple germination test to confirm the seed’s viability. This involves taking a representative sample of kernels, placing them on a moist paper towel, rolling it up, and keeping it in a plastic bag at room temperature for about seven days. Counting the number of healthy seedlings provides the germination percentage, allowing you to adjust planting rates if the viability has dropped.