URBANA, Ill. – The time for sweet corn harvest is almost upon us. One of the challenges to picking sweet corn is determining its readiness. The common time-consuming method of peeling back the husk can pose problems: if the corn is not ready, removing its protective covering can allow easier entry for pests like insects and birds. So, how can gardeners tell when it’s time to harvest sweet corn without peeling back the husk?
“Sweet corn is picked when the kernels are smooth and plump. When pierced with your thumbnail, the juice of the kernel appears milky. This is called the milk phase. Milk phase occurs approximately twenty days after the appearance of the first silks,” says University of Illinois Extension educator Elizabeth Wahle.
One signal that sweet corn is ready for harvest is the drying and browning of the silks. Ears harvested before this stage will be small in diameter, have poor tip fill, and have kernels that are watery and lacking in sweetness. “At optimum harvest maturity, tips should be full and the unhusked ears should feel firm to the touch,” Wahle says.
Sweet corn generally produces at least one ear, and if growing conditions are ideal, some cultivars may produce a second ear. The second ear is typically smaller and develops later than the first ear.
Regular sweet corn cultivars, known as normal sugary (SU) types, require careful harvesting and handling to preserve sweetness and flavor. This type accounts for many of the older cultivars and has a traditional sweet corn flavor and texture. These cultivars lose their sweet flavor very quickly after harvesting, so they should be consumed immediately to take full advantage of their flavor. Silver Queen is a white SU cultivar that is a favorite among gardeners.
Modified sugary sweet corn cultivars, also known as sugar enhancing (SE) types, have higher sugar content in the kernel. This type is most common in local markets because the sweetness lasts longer, and the kernels are easy to chew, with a creamy texture and a good corn flavor. A favorite among gardeners of this type is Ambrosia, which produces a bicolor ear known for its excellent flavor.
Supersweet (SH2) corn can have two to three times the sugars of the regular SU types. The kernels are characterized by high sugar content and a very crisp texture. The conversion of sugars to starch is also much slower, making this type more suitable for longer storage and long-distance shipping. One all-American selection of this type is Honey ‘N Pearl, a bicolor known for its large ears and excellent holding ability.
“You may come across unsightly fungus with black spores, known as corn smut, in your sweet corn harvest and be tempted to toss out the impacted ears,” Wahle says. “But one person’s disease is another’s delicacy: corn smut can be an unexpected ingredient in your summer kitchen. Many Mexican cuisine cookbooks include recipes for huitlacoche soup, a wonderful delicacy with a mushroomy flavor.”
Regardless of the type of sweet corn you choose, or how you prepare it, this summertime treat is sure to be a crowd-pleaser.
University of Illinois Extension