The temperature dropped to 27 degrees F in the early morning of May 9 in the area where the Corn Watch ’20 field is located. The field wasn’t planted yet, but the operator had other fields planted. In fact, the Corn Watch ’20 crew began flagging when plants emerged on one of his fields planted April 20. It was a trial run for doing the same thing on the Corn Watch ’20 plot later. Plants that emerged the same day were marked with a flag of a specific color.
The first plants emerged 14 days after planting, and the last ones emerged 21 days after planting. The freeze occurred at day 20, when most plants had broken the surface. Because it had been cool and wet, most were yellow to pale green and hadn’t yet unfurled.
The freeze may have affected their color somewhat, but 10 days later, it was obvious they were on their way to becoming full-fledged corn plants. “We saw a few with some curled leaves here and there in the field, but it looks like about a 95% stand,” the operator observed on May 19. “It’s definitely a keeper.”
Dave Nanda, director of genetics for Seed Genetics Direct, which sponsors Corn Watch ’20, isn’t surprised that the plants survived. “As long as the growing point below ground didn’t freeze, we knew plants would recover,” Nanda says. “The growing point is the key.”
Other observations about corn, cold temps
Bob Nielsen, Purdue University Extension corn specialist, noted after the freeze was predicted but had not yet occurred that the key would be the growing point. In articles published before the freeze, he said in theory, it might be possible for a 28-degree freeze lasting up to two hours to kill the growing point below the soil surface. He said this would more likely occur if the soil were dry.
However, based on Nielsen’s observations several days after the May 9 freeze, it appeared that in most cases, the growing point below the surface wasn’t affected. Even with corn plants that were larger and had leaves unfurled, the leaves may have been frosted away, but the plant remained alive.
It’s important to wait three to five days to see if corn will recover after damage caused by an event like a frost, freeze or hail, Nielsen notes. You may need to wait longer if it is cool after the event, which it was in this case. However, within a few days, there was evidence of regrowth in most fields.
The Corn Watch ’20 field was planted on May 13, after the freeze. By then, temperatures had warmed up considerably, although there were still some days with high temps below normal. Early indications are that the later-planted corn will emerge faster than the April 20-planted corn.
Emergence day by day will be flagged in the Corn Watch ’20 field as well. In fact, there are two hybrids planted in the field, and the goal is to track emergence for both. Look for these reports in the future.