Refrigerate, cook or process corn quickly after picking to minimize sugars converting to starches.
Sweet corn is one of my wife’s favorite vegetables. But as a gardener, I avoided it—it took up too much precious garden space and wasn’t worth the effort.
When my wife was pregnant two years ago, I decided to plant it as a treat for her. While her pregnancy flourished, my corn crop was a total failure. That was a year of excessive rain, and my crop blew over in a storm, producing less than half a dozen wormy ears. Never shying away from a gardening challenge, I tried again last year, and we were blessed with a bumper crop—enough to feed our growing family, freeze some, give away more, and even sell a few dozen ears.
With the tips here—and a little cooperation from Mother Nature—you can find equal success growing sweet corn.
The many varieties of sweet corn can make your choices overwhelming.
Tips for growing sensational sweet corn
People often have preferences in kernel color—yellow, white or bicolor—but color doesn’t impact sweetness or quality. For real old-fashioned flavor, try the heirloom varieties Golden Bantam (yellow) or Country Gentleman (white).
Modern hybrid varieties are divided into three categories based on sweetness: normal sugary (su), sugary enhanced (se) and supersweet (sh2).
Sugary varieties are favored by many gardeners for their traditional corn taste, but their sugars convert to starches rapidly after harvest, decreasing quality. Varieties include Merit (yellow), Silver Queen (white) and Sweet G90 (bicolor).
Sugary-enhanced varieties—such as Bodacious (yellow), Silver King (white) and Ambrosia (bicolor)—have increased sugar content, creamier kernels and slower sugar-to-starch conversion, meaning ears will stay fresher longer.
Supersweet types have the highest sugar content and longest storage potential, but some gardeners say they are too sweet or don’t have good “corny” flavor. Supersweet varieties include Mirai (yellow), Ice Queen (white) and Xtra-Tender 282 (bicolor) and should not be planted in cold soil.
For home gardens, it’s best to plant only one variety at a time to prevent unwanted consequences from cross pollination.
My grandfather used to tell me, “Plant corn when the white oak leaves are the size of a mouse’s ear.” Amazingly, his “old-timey” observation matches the minimum soil temperature for planting almost exactly.
Plant sweet corn as early as possible in the spring to avoid pests like the corn earworm and fall armyworm, but not before the soil temperature has reached 55 F (above 65 F for supersweet varieties). The first planting can typically be from March 10 on the coast to April 15 in the Upstate. Later plantings are fine. To ensure a consistent supply of fresh sweet corn, sow successive plantings about two weeks apart, until mid-July for a fall harvest.
Corn is wind pollinated, so plant it in blocks—three to four short rows— to improve pollination and reduce falling over. Space rows 3 feet apart, with 10 inches between seeds. Follow soil test results for pre-plant fertilization and side-dressing.
Control weeds with shallow hoeing or tilling, or mulch with clean straw or shredded leaves. Drought will lead to small, unfilled ears; you may need to irrigate during tasseling and ear development. Drip irrigation is the most efficient method and results in fewer diseases.
Harvest time offers the most opportunity for error. Pick too early and the ears won’t be filled; pick too late and the kernels will be tough and starchy. To judge your harvest date, refer to seed catalogs or packets for days to maturity. Most varieties mature 60 to 100 days after planting.
Check your crop about seven days before its maturation date, and harvest when the silks are dry and brown. Your fingernail should easily pierce a kernel, releasing sweet, white milk. Harvest in the cool of the morning. Refrigerate, cook or process immediately, because sugars convert to starches rapidly after harvest if not cooled.
S. Cory Tanner is an area horticulture agent and Master Gardener coordinator for Clemson Extension based in Greenville County. Contact him here.
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Get More
For more sweet corn information and recipes, visit Clemson Extension’s Home & Garden Information Center online at clemson.edu/hgic.