Sweet Corn Types & Isolation Requirements

Sweet corn is divided broadly into two types: sweet and super sweet. Within these two main types, there are five sub-types to be aware of. Corn type affects flavor, texture, storage potential, and isolation requirements when growing, so it’s important to know the types when you are selecting varieties to grow.

Sweet Corn

The three sweet corn types are Normal Sugary, Sugary Enhanced, and Synergistic.

• Normal Sugary (su)

  Normal sugary (also called standard sugary) corn has an old-fashioned corn flavor. The sugars convert to starch rapidly after picking which means the storage potential for these varieties is only 1-2 days. This is an open-pollinated type and is not as uniform or tender of as today’s hybrids. While many people enjoy the old-fashioned chewiness and taste, we suggest trying this type on a smaller scale if you’re unfamiliar with it. Our old-fashioned corn variety is ‘Double Standard’.

• Sugary Enhanced (se) and (se+)

  Sugary enhanced corn has a four-gene trait that modifies the (su) or (sh2) gene. The result is increased tenderness and sweetness. Conversion of sugar to starch after picking is slowed for slightly better storage potential than (su) types, if stored at around 32°F. Sugary enhanced varieties have the traits from both parents and hence are “heterozygous se”; (se+) varieties are hybrids between two (se) parents, or “fully sugary enhanced,” and are sweeter. Our sugary enhanced variety is the (se+) ‘Sugar Buns’.

• Synergistic (syn)

  Each synergistic ear has 75% (se) kernels and 25% (sh2) kernels. The sweet taste blends (se) tenderness with (sh2) crispness. Allow the kernels to get plump before picking. Given the conversion of sugar to starch after picking is even more slowed, (syn) types can remain sweet and crisp for up to 5 days when stored at around 32°F. Our (syn) varieties are: ‘Allure’, ‘Essence’, ‘Illusion’, ‘Latte’, ‘Montauk’, ‘Quick Start’, and ‘Temptress’.

Super Sweet Corn (sh2)

Super sweet corn is sweeter than most other corn types. Its sugars are converted to starch at a slower rate than other types following harvest, which means it can retains its sweetness and crisp texture for several 5-10 days after harvest if stored at around 32°F. Traditional plant breeders are constantly working to improve super sweet corn and developing new varieties. Breeding work primarily focuses on genes identified as contributing the favorable flavor and texture we know in super sweet corn. Among these naturally-occurring genes in super sweet corn is the shrunken-2 gene (sh2), which refers to the shriveled appearance of the dried seeds. Johnny’s offers a large assortment of super sweet corn varieties.

Isolation

Some types of corn should not be allowed to cross-pollinate with each other during the growing season because the cross-pollination can cause poor flavor and starchy, tough texture. Super sweet corn should be isolated from all other types of corn and synergistic corn should be isolated from both super sweet an dry/popcorn.

Isolation can be achieved using planting distance or days to maturity, or a combination of both. If you grow corn varieties that need to be isolated from one another, you can do so by using one of the following methods:

1. Planting varieties at least 300 feet from each other.
2. Stagger plantings by at least twelve days and separate each planting by at least 25 feet.
3. Referring to days to maturity (DTM), plant varieties that will mature at least 12 days apart and separate each planting by at least 25 feet (e.g. Planting 'Kickoff XR' (67 days) and 'Montauk' (81 days), at the same time and 25 feet apart).

Learn More

• Sweet Corn Varieties  • Comparison Chart (PDF)
• Old Fashioned Sweet Corn • Key Growing Information
• Sweet Corn  • Key Growing Information
• Super Sweet Corn  • Key Growing Information
• Super Sweet Varieties • Growing Instructions  • Tech Sheet (PDF)