Corn Production - Classes of Sweet Corn
Sweet corn is a warm-season crop grown for commercial production in many areas of Utah. There are several common classes of sweet corn available differing in sweetness, color (yellow, bicolor, or white), and storage characteristics. The sweetness classes include standard, sugar enhanced, shrunken, and others.
Sweet corn varieties are grouped by classes, depending on sweetness, color, and storage characteristics.
Standard sugary is the oldest and most vigorous class of sweet corn. Example varieties include ‘Earlivee’, ‘Honey & Cream’, ‘Jubilee’, and ‘Silver Queen’. This class is often used in processing and sometimes sold fresh from heirloom and organic operations. A limitation of standard sweet corn is that the kernels contain less sugars and they convert sugars to starch within a few days after harvest so it must be consumed or processed quickly.
Sugar enhanced corn is also commonly known as sugary enhancer or EH sweet corn (e.g. ‘Sugar Buns’, ‘Bodacious’, ‘Fantasia’, ‘Luscious’, ‘Miracle’, ‘Temptation’). It is primarily grown for direct retail sale or wholesale market. It offers a more tender and creamy texture than other sweet corn classes. Kernels have more sugar than the standard types so storage life is extended a few days over less sweet types.
Shrunken - 2
Shrunken-2 sweet corn gets its name from the seed having a wrinkled appearance and is also referred to as shrunken, super sweet, ultra sweet, or extra sweet (e.g. ‘Devotion’, ‘How Sweet It Is’, ‘Obsession’, ‘Vision’, ‘Xtra-Tender’ series). Up to 90% of corn sold for fresh consumption is the shrunken-2 variety. Sugar levels in this class of corn are up to twice that of other sweet corn types. Additionally, the conversion of sugar to starch within the kernels occurs at a slower rate, so varieties can be stored for 5 to 10 days. A common complaint, especially about older varieties, is that the skin covering the kernels is tough. Kernels of newer shrunken-2 varieties are less tough. Seeds may germinate poorly in cold soils and should be planted after soil temperatures are optimal.
Synergistic and others
Synergistic and other new varieties (e.g. ‘Cameo’, ‘Gourmet Sweet’, ‘Vitality’) are continually being released. They are bred using combined genetics of other sweet corn types to enhance quality. Recent reports from the Midwest indicate many newer varieties perform reasonably well and are of good quality. However, some varieties, especially some of the initial introductions, have limitations including:
- Poor germination, especially at temperatures below 60°F.
- Brittle seed that can be easily damaged with rough handling.
- Smaller seed that may not work with seeding equipment.
- Poor vigor in cold conditions.
- Lodging (wind blowing cornstalks over).
- Low yields.
Consult local seed dealers for varieties that best fit your needs.
Isolation is necessary to maintain kernel sweetness and color. All sweet corn varieties should be isolated from field corn by 250 feet or 14 days-difference in pollen shed (tasselling dates). Isolate shrunken-2 varieties from standard and sugar enhanced types to minimize starchy kernels. While isolation of sugar enhanced from standard types is not necessary, it does ensure full expression of the different sweetness characteristics of the variety.
To maintain kernel color, white varieties need to be isolated from yellow or bicolor corn. Yellow is the dominant color so pollen from yellow corn will cause fewer white kernels in both bicolor and white varieties. However, white pollen does not influence color formation in yellow or bicolor varieties.
Sweet corn is a warm-weather vegetable. Germination and growth start at 55°F and the optimum temperature range is 70 to 86°F. To avoid seed rot and to maximize germination, soil temperatures at planting time should be at least 60°F. When soil temperatures at planting are below 75°F, it is recommended to use seed that has been pretreated with a fungicide to reduce loss of seed due to rots.