Week 12 - Troubleshooting Sweet Corn

For episode/article 12 for This Week in the Garden, we’ll troubleshoot some common problems with sweet corn. Sweet corn is a favorite in many gardens, but can be frustrating when things don’t turn out the way you’d like. In this article/vlog, we’ll go over some of the things you might be seeing with your corn and what you can do to prevent it in years to come.

We’re going to start at the beginning with poor germination. This is a problem I had this year and there are a number of reasons why this might happen. The first is planting depth. Corn seeds only need to be planted about an inch deep. If you plant the seeds too deep they might not come up, while if you plant them too shallow they might wash away. One way to tell if you’re having issues with planting depth is to see when the seeds emerge. If the seeds pop up all within 2 or 3 days, you’ve done a good job. Another reason you might get poor germination is cold soil temperatures. Sweet corn needs soil temperatures around 65 degrees. Anything colder will prolong the germination time and can result in the rotting of the seeds. The last reason for germination issues is over or under-watering. I like to try to keep the seeds watered once a day until they germinate. This prevents the new, fragile roots from drying out.

Once the plants have emerged, the next issue people run into is the wind blowing over the corn. There are a number of reasons for this, and even if you do everything properly, a strong wind might still blow everything down. The first reason corn might blow down is the soil it’s planted in. Unfortunately, there’s not much you can do about this one. Sandy soils can be difficult to grow corn on as they’re loose, making it easier for the corn easier to fall over. The other reason corn might fall over is if it has shallow roots. Corn will develop shallow roots if it has been overwatered, or if it was planted too shallow. Overwatering prevents the corn plant from sending roots down deep into the soil in search of water. This leads to a smaller root system and a less sturdy plant. Corn can tolerate dry weather, so once the plants have emerged, reduce your watering to once or twice a week depending on the rain.

After the plants have been growing a while, you may notice the corn is tasseling, but the plants are short. This has been a common problem this year for a number of reasons. The first reason your plants may be shorter than expected is due to the variety. In general, plants that reach maturity quicker, like 60 and some 70-day varieties are going to be shorter plants. Another reason plants may be short is lack of nutrients. Corn needs a lot of nitrogen. Our recommendation is about 200 lbs/ acre! In years like this year, where we’ve had a lot of rain, the nitrogen that has been put down has likely been washed away. You’ll notice nitrogen deficiencies as yellowing of the leaves. For more information, check out our video on nutrients from a few weeks back. The last reason corn might be short is cool weather. This year, especially early in the summer, has been cool. Corn reaches maturity based on how many heat days it experiences. This year was cool in late April and early May, and so some corn around the county has been delayed a few weeks and is much shorter than normal.

A few weeks after tasseling corn should be ready to harvest. At this time, an issue you might come across is poor pollination. This will look like ears that are not completely full or kernels that are irregularly sized. There are a number of factors that relate to pollination. The first reason you might have issues with pollination is if you have too few tasseling plants. Corn is pollinated by the wind, and so if the plants are too far apart or too few, they won’t pollinate well. Another reason for poor pollination is hot weather. Days, where the high is above 90 degrees, will damage the corn’s pollen, resulting in poor pollination. Planting corn earlier in the year, or planting early/late-maturing varieties can help avoid some of the hottest summer days.

The final issue you might come across is when you’re eating your corn and that’s tough/ unsweet corn. Variety can play a big role in the sweetness of the corn. There are three main types of sweet corn: standard, sugar enhanced, and supersweet. If your corn isn’t as sweet as you’d like, check to see which category your corn falls into. For more information on this, check out this article from Iowa State University. Another reason your corn might not be sweet is due to cross-pollination with field corn. Field corn has a higher starch content and if a field is located close to your corn, can pollinate your sweet corn. Try to plant as far away from field corn as possible, or place your corn behind barriers such as fences or shrubs to reduce the cross-pollination. The last reason your corn might not be sweet is if it is over-ripe, or picked improperly. We made a video a few weeks back on proper harvest and storage. For sweet corn, harvest once the tip kernels have filled and always harvest in the morning. In the morning the corn has a higher moisture content and will be sweeter than corn harvested in the afternoon.

Those are a few of the more common problems people run into when growing sweet corn. If there’s anything that you’ve seen in your garden that you’d like to know more about, fill out our question form, or shoot me an email to let me know.

That’s all for this article from This Week in the Garden. If you’ve missed any articles, check out our website where we keep them archived and fill out our form if you have any comments or questions. Of course, stay tuned until next time for This Week in the Garden.

-Adam