In about a month, many corn plants across Indiana will begin to make a familiar change. Tassel emergence indicates one of the most critical periods in development that determines yield. Significant stress from heat and drought during this period can result in more yield loss than at almost any other time.

Corn plants contain both male and female flowers on the same plant, with the tassel representing the male flower, and the silks representing the female flower. A single corn plant can produce from 2 million to 5 million pollen grains per tassel. If you walk a cornfield, this will become abundantly clear on your hat and shirt!

Peak pollen shed typically occurs during midmorning and late afternoon/evening with cooler temperatures. Pollen shed can be impacted by weather. Heavy dew and rain delay pollen shed. Cool, humid weather can delay pollen shed, and dry, hot conditions can accelerate pollen shed. A single corn plant takes about seven days to finish shedding pollen, with most pollen shed occurring in the second or third day. Overall, an entire cornfield can take 10 to 14 days to complete pollen shed.

As pollen is released from the anthers, the goal is to successfully transfer pollen to emerging silks to fertilize individual ovules. These are potential kernels. For a kernel to be produced, fertilization must occur.

The silking story

In many modern corn hybrids, it’s typical to see silks emerging prior to full emergence of the tassel. Over time, corn breeders have worked to shorten the time from anthesis to silking to increase the likelihood of pollination success, which can improve yields. Corn silks are only viable for about 10 days.

In addition, due to their high-water content, silks are very sensitive to water levels in the plant and drought stress. Corn water use is at its highest during this period. Significant drought stress can cause silk emergence and elongation to become delayed or even fail, resulting in poor synchronization between pollen shed and silk presence. This can result in poor kernel set and yield loss. In certain instances, low humidity and high heat can cause emerged silks to desiccate prior to pollination success.

So, weather conditions during corn pollination are critical toward achieving high yield potential and producing high yields. Corn has a very short window to successfully complete the most critical stage in the plant’s life. Therefore, any poor conditions or stress that hinders plant health and the synchronization between pollen shed and viable silk emergence can hinder kernel set and corn yield.

Poor pollination symptoms are often exhibited by missing kernels throughout the ear, missing kernels at the tip of the ear and excessively long silks. The first silks to emerge are from the butt of the ear, and the last silks emerge from the tip, making those the last ones pollinated and first ones aborted in stressful conditions.

Paying attention to the health of the corn plant and environmental conditions during this period is essential for understanding the yield potential of your corn crop.

Quinn is a Purdue University Extension corn specialist. Email him at [email protected] or call 765-494-5314.