How to Plant Sweet Corn

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It’s not unusual to see the tall, slender stalks of corn plants, topped with silky tassels swaying in gardens. They are a staple vegetable grown in many backyards across much of the United States.

It’s for a good reason too. It is generally easy to grow, plugging away in the garden without fussing or suffering from many problems. One of the biggest challenges is keeping animals like deer from trying to sneak in and munch on the sweet kernels.

If you make sure it’s planted where it gets lots of sunlight, it’s watered regularly, and fertilized a few times, you’ll be rewarded come harvest time with tender, delicious ears of corn on the cob that are perfect for your backyard barbeque.

General Information

In many parts of the country — specifically USDA growing zones 4 to 8 — sweet corn is grown as an annual crop. It loves the heat and long sunny days of summer and takes 60 to 100 days to reach maturity depending on which variety is grown. Ears develop kernels that are white, yellow, or bi-color.

Types of Sweet Corn

With over 85 different varieties to choose from, there are many options for planting in your garden. All of these different varieties can be classified as one of three types: standard (su), sugary enhanced (se), and supersweet (sh2). The different types have varying sugar levels within the kernels, seed vigor, and storage qualities after being harvested.

Standard

  • Lowest sugar levels of the three types.
  • It has what is known as traditional sweet corn flavor and texture. 
  • Ears only retain quality for 1 or 2 days in the garden once mature.
  • It doesn’t store well since the sugar in kernels is quickly converted to starch.

Sugary enhanced

  • The sugar level is medium, between standard and supersweet types.
  • Kernels are tender and easy to chew because of soft pericarps.
  • Harvest and storage periods are slightly more extended than standard types.

Supersweet or shrunken

  • Kernels have up to twice the sugar levels as standard types.
  • The longest harvest and storage period since the conversion of sugars to starches occurs much slower.
  • Yields are generally lower than standard.

Timing

Unlike some other garden vegetables, it isn’t recommended to start seeds indoors. Once the soil temperatures hit 55 ℉, it’s safe to plant outside and should be done as quickly as possible. Depending upon your climate and the type you’re growing, this could be from the middle of April to about the middle of May.

Soil Prep

A week or two before planting, remove all rocks and debris from the garden bed and work the upper 8 to 10 inches of soil. Plants require a fair amount of nutrients due to their quick vegetative growth, so incorporate 3 to 4 inches of organic matter — finished compost or well-aged manure — into the soil.

Planting

After the threat of spring frost is over, direct sow seeds into the recently prepped garden bed. Sow seeds approximately one-half to one inch deep, covering with soil. Space seeds 4 to 6 inches apart within rows, 30 to 36 inches between rows. After germination, thin seedlings to a spacing of about 12 inches between plants.

Care Guide

If you’re looking for an easy-to-care-for garden plant, sweet corn should rank highly on your “I should plant this” list. After all, farmers grow vast fields of it all the time without micromanaging its care. Like other garden plants, it needs plenty of sun, water, fertilizer, and needs to be kept free of pesky weeds, insects, and diseases.

Sunlight

To get the best possible harvest, plant seeds in a spot that gets lots and lots of full sun. Probably more so than any other garden plant. Ensure they receive a minimum of 8 hours of direct sun daily, and there’s no need to worry about shade during the hottest part of the day.

Watering

Throughout the growing season, corn needs about one inch of water per week. You may need to up this slightly if you plant in sandy soil, or are going through scorching, dry weather. When plants are being pollinated, and the kernels are forming, it’s critical to keep them well-watered to avoid water stress.

A man watering corn to allow for robust growth.

Fertilizer Requirements

Just before planting, work in 1 cup of higher nitrogen fertilizer (15-5-10 for example) per 10 feet of row, watering well. When the plants are 2 feet tall or close to knee-high, scatter a scant 1 cup of fertilizer for every 10 feet of plants between the rows and mix it lightly into the soil.

Weed Management

Once plants get some height to them, they shade the soil, dramatically reducing weed seed germination and cutting down on weed problems. But when plants are young, it’s important to keep the bed weed-free to prevent competition for resources. Carefully hoe the weeds, chopping them off just under the soil surface to avoid damaging the corn’s roots.

Some websites recommend using atrazine to reduce weeds, but take caution in doing so. The herbicide stays active in the soil for a long time and can injure the next crops or vegetables you decide to plant.

Pest & Disease Management

Plants don’t typically have problems with the usual garden pests such as aphids and whiteflies, but they are susceptible to corn earworm, European corn borers, flea beetles, and cutworms. Regularly scout for problems and treat immediately. You may also need to protect your plants from deer and raccoons, especially when the ears are close to maturation.

Stalk of corn growing weed free and pest free.

Growing Tips

Tips and tricks are always warranted when growing something new in the garden, and surprisingly they may even provide experienced gardeners with some extra, helpful knowledge. Adding one or two of the following tips — or all of them if you choose — will help you grow the best crop possible and reap the best harvest you can.

  • Plant corn in shorter rows, forming blocks instead of long sections since plants are wind-pollinated. This improves pollination rates.
  • If you miss the “target” harvest time, the flavor goes downhill quickly as the sugars are converted to starch.
  • Make sure to separate different varieties in the garden to prevent cross-pollination. Or stagger planting dates to leave about two weeks between when the varieties tassel.
  • Once plants have three to five leaves, plant another crop if you have room to have a longer harvest time.
  • In colder climates, you can warm the ground with black plastic and plant sooner.
Healthy sweet corn harvest ready to be eaten
Photo credit to Garry Knight

Companion Plants

Sweet corn is a great companion plant, dating back to the early days of American history. It is one of the well renowned “three sisters” — corn, beans, and squash planted together with each vegetable contributing a specific benefit to the other two. It also pairs well with other garden vegetables, herbs, and ornamental flowers.

The best companion plants include:

Avoid planting celery, all members of the cabbage family, and tomatoes next to your corn.

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About the author: Carley Miller is a horticultural expert at TheGreenPinky. She previously owned a landscaping business for 25 years and worked at a local garden center for 10 years.

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