Sweet corn is one of the most familiar vegetables of late summer. Most people leave it to the farmers to grow corn, but there’s no reason home gardeners can’t add this crop to their vegetable plot.
Of course, corn does take up more space than other vegetables, so you do need to have enough room to grow it. Some important growing tips will also go a long way towards having a successful harvest instead of a disappointing one.
With that in mind, here’s a complete guide to growing sweet corn from seed to harvest.
All About Sweet Corn
Sweet corn (Zea mays) technically isn’t a vegetable at all. It’s eaten like a vegetable but is actually a whole grain that belongs to the grass family (Poaceae).
Even though corn syrup has fallen out of favor recently, eating corn in its whole form provides your body with a lot of nutrients like vitamin C, phosphorus, magnesium, folate, and fiber.
Sweet corn can be a somewhat tricky crop to get right the first time. It can be grown as an annual in USDA hardiness zones 4-9, and some early maturing varieties can be grown in zone 3.
One of the things that makes things tricky is that sweet corn needs a long, frost-free growing season. This means you need to get it in the ground quickly, but you can’t let it be exposed to frost.
Sweet corn is a popular late summer crop that not many home gardeners attempt to grow. While it does take a little more planning and care than other vegetables, there’s no reason you can’t grow it in your backyard.
Corn also needs to be planted in a specific pattern because it’s pollinated by the wind, rather than by insects like most vegetables.
Harvesting time is critical as well. It’s a late summer vegetable that should be harvested before cold weather comes through. Picking corn too early will give you hard, flavorless ears, but leaving it too late causes the sugar to convert to starch, degrading the flavor.
If you’re feeling discouraged at this point, don’t worry! Once you understand how corn grows, you’ll know exactly what you need to do to plant and care for it in your garden. That’s why this guide is here.
Sweet Corn Specifics + Main Types
You may not know this, but there are three main types of sweet corn. They all have similar characteristics but differ in sweetness, texture, and storage capacity.
In general, you can expect most types of sweet corn to grow 6-8 feet tall with a 1-2 foot spread. They flower in summer and start developing kernels that become the ears of corn we harvest. The kernels are white, yellow, or a mix of the two, although ornamental types can have multi-colored kernels with purple, blue, and red mixed in.
Ornamental corn usually isn’t edible but it makes a great fall decoration. You may want to try growing some after you master sweet corn.
Sweet corn is named the way it is to designate it as a different crop than field corn, which is much starchier, harder, and typically only used for animal feed.
Different types of sweet corn have been developed over the years and are mainly designated by their sweetness level. Here’s a look at the three main types:
- Standard Sweet Corn (SU)– This can be thought of as the “original” sweet corn. It was first grown by indigenous peoples in the Americas and gradually developed a sweeter flavor as the seeds of the best-tasting corn were saved each year. Eventually, settlers, and later plant scientists, continued to develop this type until it became the standard. Standard varieties don’t store well and should be eaten within a week of being harvested.
- Supersweet (SH2)– True to its name, this is a supersweet type of corn that has on average 4-10 times more sugar content than the standard type. It was developed in the 1950s by a botany professor at the University of Illinois who discovered a specific gene in corn that produced kernels with more sugar and less starch.
- Sugar-Enhanced (SE)– This type falls between standard and supersweet as far as sugar content. It’s sweeter than standard varieties, but also keeps its texture for longer, allowing it to be stored longer after harvest. It also tends to produce the most tender corn.
Before growing sweet corn, consider the different types and decide which one appeals to you more. Of course, you can always try a different type next year!
Best Sweet Corn Cultivars
When it comes to choosing a good sweet corn variety, keep days to maturity in mind as well as flavor and disease resistance. For example, if you live in a colder region with short summers, you’ll most likely want to choose an early-maturing corn.
Choose the type and cultivar of sweet corn you want to grow based on flavor and on what grows best in your region. Picking an option with good disease resistance will save you heartache later.
Here are some of the most popular varieties:
- ‘Golden Bantam’– This is an early-maturing, heirloom sweet corn. Ears are yellow, tender, and fantastic for both fresh eating and freezing.
- ‘Early Sunglow’– This variety is another quick-maturing, sweet option that works especially well for gardeners in colder zones. Plants are on the shorter side (4 feet tall) and ears are yellow.
- ‘Silver Queen’– The queen of late-season varieties, this cultivar develops pale white ears that are richly flavored and tender. Plants are tall and have good disease resistance. An excellent cultivar if you have a long enough growing season.
- ‘Ambrosia’– This is a sugar-enhanced variety that is great for home gardens. It has the typical white and yellow kernels and a great, sweet flavor. Early to mature.
- ‘Nirvana’– This is another bi-colored cultivar that produces high yields of sweet corn with great texture and taste. A supersweet corn that’s fairly quick to mature.
- ‘Ruby Queen’– A very rare red sweet corn that has sweet, tender kernels and an ornamental blush-red coloring. The tassels, stalks, and husks also have red running through them and are very decorative.
Note: It’s best to only plant one type of sweet corn at a time unless you can separate different types by at least 250 feet. This is because corn easily cross-pollinates, which changes their characteristics, often ruining flavor and texture.
Growing Sweet Corn from Seed
Planting sweet corn correctly is key to getting healthy plants and a good harvest. You should take more care at this step than you would for many other common garden vegetables.
The best way to plant your own corn is by seed sown directly in the garden. You can start seeds indoors or buy transplants from a local garden store, but corn does not transplant well, so these methods aren’t recommended.
When to Plant Corn
Plan to put your sweet corn seeds in the ground about 2 weeks after your last frost date in the spring. Corn is very sensitive to frost, so you don’t want to plant it too early and risk losing your crop, but it also needs a long growing season, so don’t wait too long.
The soil temperature should be at least 55°F before planting corn seeds and ideally closer to 60°F. Otherwise, seeds won’t germinate.
If you are planting a supersweet variety of corn, wait until the soil gets to at least 65°F.
In colder regions where the soil warms slowly, you can put black plastic or black landscape fabric down to help it heat up more quickly. You can also plant a second round of corn a few weeks after the first to get a second harvest.
Where to Plant + Soil Preparation
Sweet corn is best grown in squares, not long rows, so pick out a section in your garden where you can plant accordingly. It should be somewhere that gets full sun and is well-drained yet can hold adequate moisture.
Though you see corn planted in long rows on farms, in a home garden, it’s better to plant it in a square or rectangle. This helps with successful pollination.
You can plan to fit 15 corn plants in a 3 x 5 foot bed and 20-24 in a 4 x 6 foot bed.
Because most of us don’t have ideal soil to work with, it’s likely you’ll need to do some amending before planting.
If you can, work compost or aged manure into your corn plot the fall before planting. This allows it to break down and get worked deeper into the soil over the winter.
If it’s too late for that, work a good amount of compost or aged manure into the soil a few weeks before planting, mixing it 8-12 inches deep.
Make sure that your amended soil drains well but doesn’t dry out too quickly (corn is picky about moisture).
How to Plant Sweet Corn
Once you have your garden bed prepared, you can head out with your corn seeds.
The reason corn should be grown in a square or rectangular bed is because of how it gets pollinated. The wind is responsible for “carrying” pollen from the tassels that come out of the tops of the plants to the silk strands of the ears further down the plant.
If you were to grow one long row of sweet corn, chances are the wind would just blow the pollen away without it touching any of your ears of corn. By planting at least 4 rows deep, the wind can easily knock pollen off from one row to have it fall on the next one in.
Though corn only needs a spacing of 8-12 inches, make sure each row has more room between it and the next one- about 3 feet. This ensures good airflow for a healthy crop.
After you’ve planned out your bed, sow your sweet corn seeds 1½-2 inches deep and 4-6 inches apart. Space each row 30-36 inches apart.
Water the area where you planted seeds well, and keep it from drying out while the seeds germinate. At the right temperature, germination should happen in 7-10 days.
Once your corn seedlings sprout, be sure to water as needed so that the soil doesn’t dry out. When they are 3-4 inches tall, thin them out to a spacing of 8-12 inches. To avoid disturbing the roots of the seedlings you want to keep, snip off the ones you are thinning at ground level.
Sweet Corn Care Guide
Another important piece of successfully growing sweet corn is to keep up with maintenance throughout the growing season.
Corn has a shallow root system, so one of the most important tasks is to keep it well-watered during dry spells. You can mulch around plants to help keep moisture in the soil and to keep weeds down.
Weeding is also important so that nutrients aren’t getting stolen from your sweet corn, but be sure you weed carefully and avoid using tools that will damage the sensitive root system of your plants.
To get full, flavorful ears of corn later, you’ll need to take care of your plants during the summer. Watering is probably the most important task followed by weeding and fertilizing.
Sweet corn is a heavy feeder and will need to be fertilized throughout the growing season unless you have very rich soil.
You can fertilize with a balanced garden fertilizer every 3-4 weeks depending on what kind of fertilizer it is. Apply the fertilizer according to the instructions on the package, and always water thoroughly after fertilizing.
Pests and Problems
Unfortunately, sweet corn does have a variety of pests that can be a problem.
There are several insects that specifically go after corn: corn earworms, European corn borer, corn root aphids, and corn sap beetles.
You can check to see which ones are more common in your area to know what you’re dealing with ahead of time. It’s also a good idea to buy sweet corn varieties that are resistant to some pests like corn sap beetles.
Corn earworms and borers are most likely to make an appearance. Earworms feed on the silk and kernels of corn, and borers will eat through the stalks and ears.
Though sweet corn does have several annoying pests that attack it, you might find your biggest nemesis to be raccoons. They like to climb the stalks and eat almost ripe corn before you get to harvest it.
Both can be treated with a Bacillus thuringiensis (BT) treatment like Thuricide, which is a natural pest control. You can cut the tips off any ears affected by earworms and eat the rest of the cob.
There are also a few bacterial and fungal diseases that can affect corn. Your best option is to buy disease-resistant varieties, practice crop rotation each year, and clean up all plant debris at the end of the season.
Dealing with Big Pests
The two biggest pests (literally) you’ll have to deal with are deer and raccoons. Both love sweet corn, especially raccoons, and they can be hard to keep away.
Fencing and placing stakes or poles throughout your garden (so that deer don’t have a landing place) is the best way to keep the deer population at bay.
Raccoons are more difficult because they climb and are small enough to sneak through holes. If it’s an option for you, put up a short fence with electrical wire at the top. Or try creative methods like playing a radio in your corn patch at night, setting up flashing lights, or covering your plants with netting.
Deer and raccoons will be most attracted to sweet corn as it starts to ripen, so be especially vigilant at this point. Raccoon or deer repellent can be helpful at this point.
How to Harvest Sweet Corn
Harvesting sweet corn at the right stage is key to flavorful, sweet ears instead of flavorless or overripe corn.
One of the best indicators that sweet corn is ready to harvest is the silk turning brown and dried-out. You can also feel individual ears before picking them to make sure they are plump.
The best way to tell your sweet corn is ready is to look at the silk tassels that stick out of each ear. When you first notice the silk appearing, plan to harvest about 20 days later. Ears are ready when the silk turns brown and looks dried-out.
Another way to tell whether an ear of corn is ready is to feel it. It should feel plump and firm, filling out the husk. You can also pull the top part of the husk back to check the kernels. They should be full and “bleed” a milky sap if you puncture one with your fingernail.
Once your sweet corn is ready, harvesting is easy.
Go out with a basket and simply twist ears downwards to break them off the stalk. If you can, harvest in the morning when the weather is cooler.
Storing Sweet Corn
Most sweet corn is best if eaten right away. If you aren’t going to eat it the same day, place ears in your refrigerator immediately after harvesting where they should keep their flavor for about a week.
Enjoy your corn soon after harvesting for the best flavor. Some supersweet varieties can be eaten fresh, and all can be cooked in your favorite recipes.
To store corn long term, the best method is to freeze it.
Before freezing it, you’ll want to blanch the ears. This is a simple process of boiling it in water for several minutes (7-11 minutes, depending on size) before quickly transferring to an ice bath.
Once the corn is blanched, you can either freeze it whole or cut the kernels off for easier eating later. To do this, use a sharp knife to slice off as many kernels as possible from each ear of blanched corn.
Store the corn in freezer safe bags or containers. It will keep its flavor for 6-12 months.
The Joy of Growing Sweet Corn
Growing sweet corn can be a tricky task, but when you get it right, you get to enjoy the freshest ears of corn possible!
You can also branch out into other types of corn like ornamental varieties and even popcorn.
To practice companion planting in your vegetable garden, try planting a trio known as the Three Sisters: corn, pole beans, and squash. This is an ancient Native American planting trick that combines three plants that help each other grow.
Corn provides a stalk for the beans to grow up. The beans fix nitrogen in the soil, which benefits the other two plants, and the large squash leaves shade the soil and keep it cool and moist.
You may be surprised at how much better your corn does when planted with its “sister” vegetables!