Sweet corn roasted on a grill and rolled in butter is one of those irreplaceable tastes of summer, and nothing beats sweet corn straight out of the garden! If you’re feeling a little more adventurous, you can even grow your own popcorn for healthy snacking, or dent corn for the freshest, most flavorful grits or cornmeal you’ve ever tasted. Read on for pointers on how to grow the best corn ever in your own backyard.
When to Plant Corn
Corn is a warm season crop that is highly susceptible to frost, so wait to plant until all danger of frost has passed and the soil has warmed up. A soil temperature of at least 60 to 65 degrees F is necessary for good corn germination. Usually this means waiting at least two weeks after your average last frost. Starting corn indoors and transplanting outside isn’t generally recommended, since the seedlings’ roots are delicate and sensitive to transplant shock. Some growers in northern climates with short growing seasons do it though. It just requires a great deal of care when handling the young plants. Check the days to maturity on whatever corn you’re thinking of growing, and make sure you have at least that many frost-free days in your growing zone.
How to Plant Corn
Choose a spot with full sun and well-draining soil. Work in a couple inches of good quality compost or aged manure before planting to ensure your corn has the nutrients it needs. Plant seeds 1-2 inches deep and 2-4 inches apart in rows 12 inches apart. Plant short rows close together in a block, not one or two long rows, to ensure full pollination. (Poor pollination results in ears with few kernels on them.) Water deeply at the time of planting. Once the plants are about four inches tall, thin them to 8 to 12 inches apart.
Another great way to plant corn is the Three Sisters method traditionally used by Native Americans for millennia. The “three sisters” are corn, beans, and squash, three crops that work together to make each other more productive. The corn provides a trellis for the beans, while the squash vines ramble along the ground shading out weeds, and the beans fix nitrogen, providing fertility for all three crops. The traditional Haudenosaunee way to plant using this method is to mound up the soil into round hills about 4 to 5 feet across and 4 inches high. Then, plant a circle of several corn seeds at the center of each mound. Once the corn plants reach about a foot tall, seed pole beans around them. Once the beans are up, seed the squash around the outside of the circle. You could also interplant beans and/or squash in between more widely spaced straight rows of corn, but planting around clumps of corn ensures that the corn is close enough together for good pollination, and to hold each other up in a strong wind.
Another important corn planting tip: Don’t plant two different varieties of corn within about 250 feet of one another if they will be tasseling (producing pollen) at the same time. Unlike for most vegetables, cross pollination can ruin a corn crop. Read our deep dive into corn pollination if you want to know the science behind that!
Caring for Corn and Preventing Pests
Corn is generally a low-maintenance crop. It does take quite a bit of water, but doesn’t like to sit in soggy soil either, so pay attention to soil moisture, particularly around the time the tassels and silks begin to emerge. Corn that goes through drought stress around the time of pollination might not get pollinated properly.
Even if your soil has been amended with compost early in the season, it’s a good idea to give your corn a boost with a high-nitrogen fertilizer when it reaches about 2 feet tall. Blood meal or fish fertilizer are good organic options. A little extra fertility will help your corn develop the best possible ears.
A number of pests can affect corn, and as with any garden crop, the best defense is crop rotation and garden diversity. Attracting beneficial insects to your yard with flowers and native plants can cut down insect pests substantially. One of the most destructive (and grossest) insect pests is the corn earworm. Rubbing vegetable or mineral oil on the tips of developing ears can discourage them from chewing into the husks. Some pests are a little larger, and furrier. Corn is unfortunately a favorite of marauding deer and racoons. Electric fencing can stop them in their tracks, but if that wouldn’t go over well in your neighborhood, spreading blood meal or human-scented items like hair clippings around your plot can help deter them too.
How to Harvest Corn
Harvesting corn is as simple as snapping the ears off the stalk with your hand (a quick, downward twisting motion works best), but knowing when to harvest can be a little tricky depending on which type of corn you’re growing.
When to Harvest Sweet Corn
Sweet corn is typically ready to harvest about three weeks after the silks first emerge. A ripe ear will have brown silks and a filled-out ear tip. Give the end of the ear a gentle squeeze, and you should feel the firm kernels right under the husk. If you have brown silks and filled-out ears, your corn is probably just about ready, but to be totally sure, test the kernels. Peel back the husk to expose some kernels about an inch back from the tip and puncture a kernel with your thumbnail. If the juice comes out milky and translucent, the ear is perfect. If the juice is clear, it’s too early, and if no juice comes out, you’ve waited too long. Once you test a few ears, you’ll get a feel for when your sweet corn is ready just by looking at it. The ideal harvest window for sweet corn, called “milk stage” only lasts 2-3 days, so keep a close eye on your corn patch when the ears are getting close to ready! Once you’ve harvested, eat your sweet corn as soon as possible. The sugars will continue to convert to starch even after the ears are picked.
When to Harvest Popcorn, Dent, Flint, and Flour Corn
Unlike sweet corn, popcorn and field corn (including dent, flint, and flour types) are harvested at full maturity, after the starches have developed and the kernels have dried out. Wait to harvest until the husks have completely turned brown. Usually this takes 100 to 120 days from planting. In dry climates, the ears can be left on the stalks even longer, until they are completely dry, but in rainier climates it’s a good idea to bring them indoors to finish drying. Many people hang the ears by their peeled-back husks for drying, or completely husk the ears and stack them on wire racks. Once the kernels are totally dry, you can shell them off the cobs with a hand-sheller. For popcorn, it’s especially important that the kernels are completely dry before you try to pop them. The most common reason why homegrown popcorn doesn’t pop properly is because of too much moisture left in the kernels. Drying your popcorn in a dehumidified indoor space, or utilizing silica gel packs to take out the last of the moisture can help if you live in a humid place.
Ready to get started growing corn in your garden? Shop our full collection of corn seeds, learn more about the different types of corn you could grow, or learn about the botany of corn pollination on our blog.Written by Sow True Seed's Agriculture Director, Leah Smith