Issue: April 13, 2002

Sweet corn

I lost my notes from an Extension Service presentation last year. In that talk Dr. Dickerson told about different sweet corn varieties, including some that were super sweet. How can I tell what varieties are sweetest?

It is time to begin planning for planting corn in New Mexico, and it is wise to consider which variety you want to plant. Dr. George Dickerson, NMSU Extension Horticulture Specialist, tells us in NMSU Extension Guide H-223, "Home and Market Garden Sweet Corn Production," that there are several varieties of sweet corn with more sugar than the older varieties. These are based on different genes in the corn. The gene for sweetness in the old sweet corn varieties was called the "su-1" gene. Sweeter varieties of sweet corn contain the "sugary enhanced" gene, "se" These are roughly twice as sweet as standard sweet corn and the sugar is more slowly converted to starch than in standard varieties. This means the sugary enhanced sweet corns start sweeter and remain sweeter longer. Another genetic variation occurs in varieties with the "sh2" gene. The sh2, or super sweet varieties are three to four times sweeter than the standard sweet corn varieties. The "sh2" means the corn kernels are shrunken (shriveled). This is obvious when looking at the seed. In the sh2 varieties, the enzyme that converts sugar to starch is also reduced, so the corn remains sweet much longer. These varieties are more sensitive to soil temperature and should only be planted when soil temperatures are above 55 degrees, and they should be planted only half as deep in the soil. They are also more influenced by pollen from other corn varieties. Pollination by other corn varieties, including sweet corn varieties, can result in starchy, rather than super sweet corn kernels. If you wish to plant several varieties in the same garden and can't provide 250 to 300 feet separation between them, then plant them two weeks apart so that one variety will not pollinate the other variety. This is most important for the super sweet varieties. Some people complain about the texture and taste of the super sweet varieties. They lack the creamy texture of the standard and sugary enhanced varieties because they contain a lesser quantity of water-soluble polysaccharides (complex sugars). They also have a tougher pericarp (outer covering) that gives them a more "crispy" texture. Unlike the super sweet varieties, the sugary enhanced varieties have the same texture as standard sweet corn varieties. If you are growing sweet corn for your own use, you can choose varieties based on texture and sweetness. If you are growing for the market or to give to friends, you should probably give more consideration to the difference in sweetness. The super sweet varieties will remain sweet much longer. Also consider the fact that the varieties containing more sugar in the seed will be more susceptible to disease organisms when germinating. For more information, you can find Dr. Dickerson's publication at the NMSU College of Agriculture horticultural publications web site at http://www.cahe.nmsu.edu/pubs/_h.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!