Harvesting sweet corn at the proper stage of maturity is essential to insure a high quality crop.
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.
Sweet corn remains in the milk stage for a short time. The weather determines the length of this stage. Sweet corn remains in prime condition for only one or two days during hot (85 F and above) weather. As the sweet corn approaches maturity, check it frequently during typical summer weather to insure high quality sweet corn.
Harvest sweet corn by grasping the ear at its base and then twisting downward. Use or refrigerate sweet corn immediately as its quality rapidly declines after harvest. Standard sweet corn varieties may lose 50% of their sugar within 12 hours of harvest if not refrigerated. Sweet corn can be stored in the refrigerator at 32 F for 4 to 8 days. New high sugar varieties are slower to convert sugar to starch and may be harvested over a longer period of time. The high sugar types also have a longer storage life.
This article originally appeared in the July 11, 1997 issue, p. 107.