Sweet corn is a variety of corn plants with a high sugar content eaten as a vegetable and not a grain like other types of corn. Sweet corn is also harvested prematurely for baby corn. Regardless of when you harvest corn, knowing when to plant sweet corn is crucial to having any corn yield.
If you’ve never looked into the different types of corn before, you might be surprised to learn that not every field of corn you drive past is the same. Field corn has a high starch content and is used to make corn chips and cornbread. Sweet corn has a sweeter taste and is grown to eat without manufacturing into another type of product.
After harvest, sweet corn is either sold as cobs, frozen kernels, or canned, but if you start growing corn in the home garden, by knowing the best time to plant sweet corn, you’ll have fresh sweet corn for your next family gathering.
Sweet Corn Growing Season
While there is no universal time for when to plant sweet corn seeds, the rule of thumb for every growing zone is to plant corn seeds once the soil temperature is at least 60°F. To plant super sweet corn, wait until the soil temperature is at least 65°F, as super sweet varieties prefer warmer temperatures.
When to Plant Sweet Corn Seeds
Corn is a warm-season crop, so it is best to wait for all danger of frost to pass before sowing corn seeds in the garden. Sweet corn plants tolerate light frosts and quickly recover from frost damage in the early stages when the plant’s growing point is beneath the ground.
Once young plants develop at least six visible leaves, your plant begins to suffer if temperatures remain below 30°F for more than a few hours. To avoid frost damage, start by growing sweet corn indoors.
Planting sweet corn seeds indoors provides you with better control over soil temperature and allows you to monitor your plant’s growth better before you repot a corn plant or transplant it outdoors.
The downside to growing sweet corn varieties inside first is that corn plants do not typically transplant well due to the stress of moving from a container to the garden bed. Start growing corn in a biodegradable pot of peat moss to avoid transplant shock.
Knowing when to plant sweet corn seeds depends on the corn variety you’re growing. A general guideline is to start sowing regular sweet corn seeds four to five weeks before the last frost date in your area. If you grow sweet corn early varieties, this timeline may differ based on when you expect to harvest.
Standard sweet corn cultivars are types of corn that contain less starch and more sugar than the kind of corn used to feed livestock. This corn is best eaten right after harvest when it begins its conversion of sugar to starch.
Sugar extender corn varieties like Kandy Korn contain more sugar than standard types and retain their sweetness for four days following harvest. They are less hardy than standard sweet corn and do not hold up well to mechanical handling.
Supersweet corn contains up to ten times as much sugar as standard corn types. If stored properly, this corn retains its sweetness for up to ten days. This type of corn is the most high maintenance as it requires higher germination temperatures, specific planting depth, and isolation from other types of corn to produce the best ears.
When to Plant Sweet Corn Based on Growing Zones
We suggest staggering your planting schedule to avoid harvesting all your corn at once to enjoy fresh corn throughout the sweet corn growing season. Harvest and enjoy your corn with delayed planting before your next batch is ready for harvest.
Corn grows in hardiness zones three to eleven. For the coolest of its applicable zones, when to plant sweet corn in zone 5 and below is by sowing seeds in the middle of May through to the beginning of July. With the right timing, you can enjoy corn throughout the latter part of summer and have your harvest in time for Labor Day.
Zones 6 and higher have a little different timeline. When to plant corn in zone 6 is also different than in zone 8 or 9. If you’re wondering when to plant sweet corn in zone 6, planting corn seeds starts indoors within the four weeks between the end of March and mid-April.
The average last frost date for this part of North America is around May 15th, which gives your corn seeds enough time to develop before you move them to their permanent home in the garden.
Growing corn from seeds starts in the garden in late May if you aren’t starting indoors. Starting in May allows even slow growers time to reach maturity before summer ends. With the proper planting schedule, you can even enjoy corn until the end of the growing season.
The average frost date is around early to mid-April for zone 7. When to plant sweet corn in zone 7 is in late April and early May. Start sowing seeds for the warmest zones in March once the soil reaches the right temperature.
Caring for Corn Plants
Keep your corn plants well-watered as they grow, especially when the kernels form. Because corn plants cannot handle competition for soil nutrients, add a layer of organic mulch around your plants to keep weeds from growing and reduce the chances of corn bugs invading the corn. Once your plants reach two feet tall, apply one cup of fertilizer for every ten feet of garden rows.
While growing corn, some common pests that target your plants are corn earworms, the European corn borer, and cutworms. Worms are easy to deal with by adding a drop of mineral oil into the top of the ear to suffocate any pests hiding inside the ear of corn.
Corn smut is a disease that affects all parts of the corn plant; however, the disease is most damaging to the ears of corn. This infection is common in drier climates and fields with high levels of nitrogen in the soil.
Corn smut infection causes growths to develop on the plant, making the plant inedible. There is no cure for corn smut, so remove the affected plant to save the rest of your crop if you notice signs of corn smut. If you know corn smut is common in your area, purchase treated resistant seeds.
The best time to plant corn is early in the season with fast-maturing varieties. Wait a few weeks after planting your first seeds to plant another batch to get the most corn out of the sweet corn growing season.
If you learned when to plant sweet corn with help from our guide, please share this article about the sweet corn growing season with your fellow gardeners on Facebook and Pinterest.