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Where is the Corn?

Walking through the cornfield in front of our house last week, my farmer husband and I found plenty of cornstalks but not many ears of corn. The ears we did find were either undersized or missing most of their kernels.  

We were lucky to get the corn planted at all. The planter should have been running in late March or early April, but fields were to wet. When it dried enough to plant, it was late April. Here in North Carolina, we can plant corn until May 15 and still make a crop. The earlier you plant, however, the better, so corn is tasseling in late May or early June before it gets to hot. So what happened to the corn?

Most likely our corn didn’t mate.

Corn, like all members of the grass family, has both male and female reproductive structures on the same plant, but in separate places. At the top of the plant is the tassel, the male, which produces two to five million grains of pollen. Farther down the stalk is the female flower, the ear. The silk, which I just thought was there to frustrate me when cleaning corn, actually is vital to corn reproduction. Silks are the path for the male reproductive cells to reach the ovules, also known as the kernels.  

Since the two partners are so far apart, corn is usually cross-pollinated. Their pollen is spread by wind, so the silks of one plant are usually pollinated with pollen from another corn plant in the field.

If all goes well, the tassel will develop. Starting at the bottom of the ear, silks will emerge. Pollen will be released over the course of five to eight days (sometimes up to two weeks), and the silks will capture it.  The pollen moves down the silk to the ovule and fertilization takes place. 

But what happens if all doesn’t go well? 

Dry weather can cause yield loss, meaning there will be less harvestable corn, at any time in the growing season. This year, our corn has certainly been under stress. For a good part of the season, the stalks were curled up during the day, the plant's natural resistance to dry weather, as you can see from the photo below.

Drought stressed corn
 

Pollination and silking have the most impact on how many harvestable kernels a plant will make. Drought combined with high temperatures during silking can result in 100% loss of corn. The stalks will be standing, but they won’t have any ears.  

Stress may cause the silks to be delayed or dry up early. If this happens, the pollen gets there but has no way to reach the ovule. Or, silk emergence will slow down, which could lead to fertilized ovules at the bottom of the ear but unfertilized ones at the top.

A stressed plant may shed pollen early. When this is the case, by the time the silks are ready to accept it, there’s no pollen left. Hot, dry weather can decrease the pollen’s viability or the length of time pollen is shed. Temperatures above 90˚F. can damage pollen; above 100˚F. can kill it.  

Corn tries to fight hot, dry weather by pollinating during the early morning hours or late in the evening when temperatures are usually cooler. This summer, when corn should have been mating, temperatures here in North Carolina were in the upper 90s and we hadn’t had rain in weeks. The perfect combination to keep corn from mating.  

Click here for a more detailed explanation on corn pollination.

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