One of the pure pleasures of summertime in Iowa is eating sweet corn fresh from the garden or farmers' market. Gardeners have questions when it comes to getting the ears from field to plate. ISU Extension specialists offer answers to those questions; to have additional questions answered, contact the experts by emailing or calling the ISU Extension horticulture hotline at firstname.lastname@example.org or 515-294-3108.
Sweet corn should be harvested at the milk stage. At this stage, the silks are brown and dry at the ear tip. When punctured with a thumbnail, the soft kernels produce a milky juice. Over-mature sweet corn is tough and doughy. An immature ear will not be completely filled to the tip and the kernels produce a clear, watery liquid when punctured.
The harvest date can be estimated by noting the date of silk emergence. The number of days from silk emergence to harvest is approximately 18 to 23 days. Prime maturity, however, may be reached in 15 days or less if day and night temperatures are exceptionally warm. Most hybrid sweet corn varieties produce two ears per plant. The upper ear usually matures one or two days before the lower ear.
Harvest sweet corn by grasping the ear at its base and then twisting downward. Use or refrigerate sweet corn immediately after harvest. Optimum storage conditions for sweet corn are a temperature of 32 F and a relative humidity of 95 percent.
Poorly filled ears are often the result of poor pollination. Hot, dry winds and dry soil conditions may adversely affect pollination and fertilization and result in poorly filled ears. Water sweet corn during pollination if the soil is dry. Improper planting may also affect pollination. Corn is wind pollinated. Plant sweet corn in blocks of four or more short rows to promote pollination.
The most effective way to prevent damage to the sweet corn crop is to encircle the area with an electric fence. A two-wire fence with one wire 4 to 6 inches above the ground and the other at 12 inches should keep the raccoons out of the sweet corn. Mow or cut the vegetation beneath the fence to avoid electrical shorts. To be effective, the electric fence should be installed about two weeks before the sweet corn reaches the milk stage.
The small size of “baby” corn suggests that it’s a special variety. However, most baby corn is actually grown from regular sweet and field corn varieties. The ears are harvested when they are 2 to 4 inches long and one-third to one-half inch in diameter at their base. Most corn varieties reach this stage one to three days after the silks become visible. While many sweet and field corn varieties are suitable for baby corn production, there are a few varieties, such as ‘Babycorn’ and ‘Bonus,’ which are grown specifically for the miniature ears.