You can get a hail storm on three-leaf corn and odds are it will grow back. It may even live up very close to its yield potential. It's all because the growing point of corn stays below the ground until about the five to six-lead stage, says Dave Nanda, Crops consultant, Indianapolis.
As long as the growing point is below the ground, the corn can put out new leaves and survive. Right now many fields in the Midwest are reaching that stage where the growing point either just emerged, or is very close to emerging from below ground. After that, leaves lost to hail or some other calamity won't regrow.
A clear demonstration of that occurred in the strange Midwest mid-June frost in the early 1990's. Corn wasn't as tall as it will likely be by that point this year, but it was either at or just past the point where the growing point emerges. In the wake of the frost, farmers quickly found out which fields were at the stage where the growing point had already emerged. Those fields were damaged more heavily. If the growing point hadn't yet emerged and as long as dead leaves didn't twist so tightly above the whorl that the growing point couldn't emerge, many of those fields recovered and yielded remarkably well, considering what happened to it earlier.
Researchers have even taken weed –eaters to corn at small growth stages to mimic hail damage and see what happens. It's often demonstrated for visitors to the Purdue University Diagnostic Training Clinic held at the Purdue Agronomy Research Center each summer.
Leaves are shred with a weed-eater, sometimes to ground level. As long as the growing point hasn't emerged, the corn typically comes back. Bob Nielsen, Purdue University corn specialist, has demonstrated this phenomenon several times in training sessions over the years.
Soybeans don't have the same luxury. Since they are a legume, their growing point immediately comes above ground as the crop emerges. So whatever affects plants at that stage has just affected the crop of the season. If soybean plants are injured and lose their leaves and stem, all the way to the ground, no matter at what stage, they're more than likely finished. It's one of the physiological differences that separate the two crops.