In this posting, I'll describe the historical development of sweet corn and describe various the various categories that are available to home vegetable gardeners.
The History of Sweet Corn
Corn has been cultivated in the Americas for somewhere between 8,000-10,000 years. For most of that history, the corn grown was high in starch and low in sugar. Generally referred to today as "field corn," this type of starchy corn is traditionally used to make a variety of foods such as corn bread, tortillas, tamales, polenta, and hominy. It is also used as fodder for animals. (For more information about these starchy corn varieties, check out my posting on dent and flint corn)
Sweet corn is a naturally occurring mutation of field corn. A change in just one gene within the corn plant results in an increase of sugar content from 4% in field corn varieties to over 10% in most modern sweet corn.
There is debate among scholars as to when this mutation occurred, but at least some scholars believe that the first sweet corn mutations occurred over 1,000 years ago in the area around Peru and Bolivia. Research done by Paul Frederick on the growth of the New England Corn Industry suggests that native Americans in the U.S. also cultivated some sweet corn, but it was not a particularly important crop relative to field corn varieties. Frederic's explanation for this is that native peoples were less interested in growing sweet corn because it is less hardy than field corn and because the sweetness declines rapidly once the corn has reached maturity, thereby eliminating any flavor advantage of sweet corn over field corn. In other words, from the perspective of flavor, it reverts to the flavor of field corn so quickly that the trade off in hardiness wasn't worth it.
Photo: Mayan Corn God
According, A. T. Erwin who wrote a book about the history of the canned corn industry, sweet corn as we know it today has it's origins in New England. Erwin believes that sweet corn was introduced into Plymouth, Massachusetts by the Iroquois in 1779.
Various Types Of Sweet Corn
- Sugary Corn - Sugary, or "SU" corn varieties, were the original sweet corns. These corn varieties currently have sugar content of 9-16%, a major increase versus field corn that has 4% sugar. SU corn tends to be hardy, but as mentioned above, it losses its sweetness very quickly once the corn has matured or been picked. As a result, SU corns need to be consumed immediately upon harvest, or preserved by canning or freezing. One key advantage of SU varieties is that they are able to germinate in cooler soils, so they may be a good choice for you if you are a Northern gardener. SU varieties also tend to have the tenderest kernels and some folks claim the most authentic corn taste. Common SU varieties include: Silver Queen, Country Gentleman, Golden Bantam and Jubilee.
- Sugar Enhanced - Sugar Enhanced, or "SE" corn varieties were developed at the University of Illinois during the 1950's. They have an additional gene that expresses sweetness in corn. These varieties are 14-35% sugar. Importantly, they retain that sweetness for up to 4 days after harvest or maturity. This makes SE varieties an excellent choice for home gardeners. One downside is that SE varieties are less tender than their SU cousins. Some well known varieties include: Bodacious, Kandy Korn, Maple Sweet, Tuxedo, and Peaches & Cream.
- Super Sweet - Super Sweet, or "SH2" corn was also developed at the University of Illinois in the 1950's. Super Sweet varieties have massive sugar content -- 28-44% and they tend to retain this sweetness for an extremely long period of time - up to 10 days after maturity or harvest. Fans of Super Sweet corn will tell you that kernels are crisp, while detractors view SH2 kernels as tough. Common SH2 varieties include: Illini Gold, How Sweet It Is, and Early Xtra Sweet.
- Synergistic - "SY" corn is a hybrid cross between SH2 and SE corn varieties that produces some characteristics of both. Specifically, the tenderness and flavor of SE varieties with the increased sugar content and storage capabilities of SH2 corns. Some examples include: Montauk, BoJangles, Honey Select, and Applause.
- Bt and Round Up Ready - These are sweet corn varieties that are genetically modified for use by commercial agriculture. I am listing these here because GMO's, or genetically modified organisms, are a hot topic in the news these days and because there have been reports that Bt corn may soon be available for sale to consumers at Wal-Mart. Genetically modified corn varieties are ones where an additional gene has been introduced to the plant in order to provide it with resistance to pests, pesticides or herbicides. In the case of Bt corn, genes from the bacteria Bacillius Thuringiensis are introduced to the corn plant in order to make corn toxic to corn borers, a variety of insect that damages corn crops. Round Up Ready corn is sweet corn that has been modified with the genes from Agrobacterium Sp. CP4. This gene conveys resistance to the herbicide glyphosate (Round Up). This allows farmers to spray their fields with Round Up to kill weeds while leaving the Round Up Ready corn plants unharmed. Kinda like the neutron bomb that kills people but leaves the building intact.
When you shop for sweet corn for your garden, you will be faced with color and maturity choices that cut across all the groups. So if you only like white or bi-color varieties you will be able to find some that are SU, SE, SH2 or SY. The same applies to early and main season varieties.
- Maturity - Early season varieties mature in 65-75 days while main season corn takes 75-100 days depending on variety and your climate.
- Color - Sweet corn comes in yellow, white, bi-color and in rare instances other colors such as blue or red.
Cross Pollination Issues
While not specifically related to particular styles of corn, I want to make you aware of this issue as you plan your garden. Corn is pollinated by the action of the wind taking pollen from the tassels of the plant to the silk on the immature ear.
As a result, corn crops can easily be cross-pollinated by other varieties if they are planted too close. Such cross pollination can effect the color of the corn (for example, a white corn variety will produce yellow or bi-color kernels) or the flavor and texture of the corn can be negatively impacted (For example, SH2 varieties that are cross pollinated end up very tough and starchy).
A general rule of thumb is to separate corn varieties by either time or distance. If you are growing two varieties, select ones that mature at different times - for example a 70 day variety and a 90 day variety. Tassel formation and pollination will occur at different times, reducing the likelihood of cross pollination between the two varieties. Alternatively, plant different varieties in fields that are 250 feet apart. There will be some cross pollination at this distance, but not sufficient to materially impact the crop. If you want to completely isolate your corn crop, separate fields by at least 700 feet.