How to Grow Sweet Corn, From Sowing to Harvest

Corn that’s had to travel miles to get to your plate will be past its peak, but cobs that have been picked in your own garden just minutes before cooking deliver a real punch of super sweet taste. FInd out how to grow super sweet corn, from sowing and planting to knowing exactly when it’s time to harvest for the sweetest, tastiest cobs.

Corn needs plenty of sunshine and rich soil with plenty of added organic matter such as compost.

If you live in a cooler climate, opt for hybrid varieties, which are usually more reliable in these conditions.

Sowing Corn Indoors

If you’re going to start seeds early, sow the seeds in pots under the protection of a greenhouse, hoop house, or cold frame. This means you can begin sowing three to four weeks before your last frost date, giving you a head start on corn sown outdoors—a huge advantage for areas with shorter growing seasons.

Sow eight to ten seeds half an inch deep into four inch-wide pots, or sow two seeds per module in a plug tray and remove the weakest of the two seedlings when they emerge. Keep the potting soil moist as they grow on.

Harden off the plants as your recommended planting time approaches by placing them outside for increasingly longer spells over the course of about a week. Plants should be at least six inches tall by the time they’re transplanted outdoors.

Planting Corn Outside

Plant corn directly outdoors once the soil temperature is about 60 degrees F. Never plant when there is still a risk of frost.

Corn requires a good deal of nitrogen for optimum growth, so work plenty of aged manure into the soil, ideally the previous fall.

Corn is wind-pollinated, so plant in blocks (not rows) for the best chance of success. If corn is not well pollinated, it will still grow but many kernels will be missing from the cob. Ideally, plant in blocks of at least four rows with 2 to 4 feet between rows.

If you seeded indoors, remove the young plants from their pot and carefully tease the roots apart, retaining as much of the soil around the roots as you can.

Or, seed directly into the ground 2 inches deep and 6 to 8 inches apart. Ensure the corn is in a place protected from strong winds.

Growing Corn

Thin the corn to stand 12 to 16 inches apart when the plants are 4 to 5 inches tall.

Corn’s roots are shallow and can easily be damaged by hoeing. Instead, weed your corn by hand for as long as you’re still able to get between the plants without damaging them.  Then, apply several inches of mulch.

Planting squash alongside corn works well, as the squash will sprawl among the corn stalks and help to suppress weeds.

Watch for signs of nitrogen deficiency (yellowing leaves) and respond with quick side-dressings of a nitrogen-rich fertilizer such as fish emulsion. 

Provide at least 1 inch of water a week.  Corn should not need supports, but it will need watering in very dry weather, especially once the tassels appear and the cobs begin to form in late summer.

Harvesting Corn

Corn is usually ready to harvest about six weeks after the tassels at the end of the ears first appear, once they have turned dark brown.

Carry out the fingernail test to make sure your corn is perfectly ripe. Peel back the top of the protective sheath and press a fingernail into a kernel. It should produce a creamy liquid. If the liquid is watery, it’s not ready yet, and if there’s no liquid it’s past its best.

To harvest, twist the ear of corn and pull it away.

Sweet corn varieties (except for supersweet varieties) lose their sweetness soon after harvest. Immediately after picking prepare the ears for eating or preserving.

So, enjoy your harvested corncobs as soon as you can. The quicker they’re cooked, the sweeter they will be!

Read more gardening tips on the Almanac’s Corn Growing Guide.

Ready to get started growing?

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