Late Spring Frost Threatens Corn and Soybeans Growth

By Scout Nelson

Warmer winter and spring conditions have allowed corn and soybean planting to begin earlier than usual across South Dakota during the 2026 growing season. As of May 17, 2026, about 80% of corn was planted, with nearly 20% already emerged, as reported by USDA, NASS. Soybean planting reached 60%, with about 10% emerged, as reported by USDA, NASS. Early planting may improve yield potential, but it also increases the risk of frost and freeze damage to young crops. Several days with temperatures below 32 degrees Fahrenheit were reported during the last two weeks, creating concerns about crop injury in many areas.

David Karki, Assistant Professor and South Dakota State University Extension Crop Production Specialist, and Jonathan Kleinjan, former SDSU Extension Agronomist, highlighted that producers should carefully evaluate fields for crop damage, especially in low lying areas where colder temperatures are more common than weather station reports. Frost occurs when soil surface temperatures reach 32°F or lower, while a freeze occurs when air temperatures reach 32°F or lower at five feet above ground level. Under certain atmospheric conditions, frost may still occur even when air temperatures remain slightly above freezing.

Mild frost events usually cause limited damage to young crops, but hard freezes with temperatures near 28°F or colder for two hours may severely injure or kill plants. Corn plants generally remain protected because the growing point stays below the soil surface until the V6 growth stage, when plants are about 1 foot tall. However, severe cold temperatures may still damage the growing point if freezing conditions continue for several hours, especially in dry soil conditions.

Soybeans are more sensitive to freezing temperatures because their growing point moves above ground immediately after emergence. Recovery remains possible if buds located at leaf nodes survive the frost event. However, plants damaged below the cotyledons will likely die.

Following frost damage, leaves may first turn black before becoming brown and dry. Producers are encouraged to wait 3 to 5 days after frosting events before making replanting decisions. Healthy corn plants usually show new growth emerging from the whorl, while soybean plants may produce new leaves from undamaged nodes. The corn growing point is located about ½ to ¾ inch below the soil surface and should appear white or light yellow and firm if healthy.

Field evaluations remain important before making replanting decisions. Good yield potential may still exist even when plant stands decline by about 20% if stands remain relatively uniform. Frost injury is often more severe in lower areas of fields where cold air settles, meaning some sections may require replanting while others continue growing normally.

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