Why Is My Corn Not Filling Out (Missing Kernels)?

Every kernel needs its own pollen grain

Each silk on an ear connects to one potential kernel, and that kernel develops only if a pollen grain lands on the silk and fertilizes it, so an ear with missing kernels is really an ear with unpollinated silks. Iowa State University Extension states plainly that inadequate pollination results in poorly filled ears. Because corn pollen is carried by wind rather than insects, the layout of your planting largely determines how well pollen reaches the silks.

This is why Iowa State recommends planting sweet corn in blocks of four or more short rows instead of one or two long rows: a block lets wind distribute pollen across many plants, while a single long row leaves many silks with no pollen source upwind. If you can shake a husked ear and the silks detach, those kernels were pollinated; silks that stay attached mark kernels that were not.

Heat, drought, and timing at silking

The pollination window is short and vulnerable to weather. Iowa State University Extension notes that hot, dry winds and dry soil conditions may adversely affect pollination and fertilization and result in poorly filled ears, and University of Minnesota Extension similarly reports that hot, droughty conditions during pollination cause missing kernels, small ears, and poor development of the ear tips. Heat and drought can dry the silks so they are less receptive and can throw off the overlap between pollen shed and silk emergence.

You cannot control the weather, but you can reduce its impact. Iowa State advises watering sweet corn during pollination if the soil is dry, which is the main lever a gardener holds during that critical stage. Combined with block planting, steady moisture through silking gives the best odds of full ears. If ears still fill poorly under good conditions, treat the cause as uncertain and check planting date, variety, and spacing with your Extension office.

Sources

Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.

• Iowa State University Extension - Growing Sweet Corn in the Home Garden — Plant sweet corn in blocks of four or more short rows to promote pollination rather than one or two long rows; inadequate pollination results in poorly filled ears; hot, dry winds and dry soil conditions may adversely affect pollination and result in poorly filled ears; water sweet corn during pollination if the soil is dry.
• University of Minnesota Extension - Dry conditions during corn pollination — Hot, droughty conditions during pollination result in missing kernels, small ears, and poor development of the tips of the ears, because drought and heat dry silks and disrupt the pollination process during the critical silking period.

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