Sweet Corn Production

Publication 7 - Also available in PDF form at http://www.wvu.edu/~agexten/hortcult/homegard/corn.pdf
John W. Jett, Extension Specialist, Horticulture

This is a very popular mainstay of home gardens, roadside and fresh markets. Although different types are popular in different areas and in different seasons, some type of sweet corn is in great demand everywhere you go. When planning next season’s corn seed order, careful attention should be paid to the kernel color desired, the genetic classes now available and finally the maturities of the varieties offered within those groups. Try to include successive plantings at intervals to have a constant supply of fresh product. A genetic revolution is taking place in the world of sweet corn these days. This species is not nearly as simple to understand as it once was and we’d like to help you sort out by genetic class the various combinations now available. They are as follows:

Normal Sugary (su) is the standard sweet corn you’ve grown through the years. You’ve enjoyed its rich corn flavor and knew that the quality was best if picked and cooked the same day. Some varieties germinate quite well at 55F soil temperatures and quality is best if isolated from field corn.

Sugary Enhanced (se) varieties have a modifying gene which increases the original levels of sugars in the kernels and extends their flavor. Moisture loss is also slower than Normal (su) and tenderness is improved. The result is a sweeter, more tender kernel with good corn flavor that will retain its quality longer than Normal (su) corn. As a group Sugary Enhanced (se) corns have similar seed weight to Normals (su) and some germinate nearly as well under the same conditions. They, too, should be isolated from field corn and are slightly better tasting when isolated from Normal (su) sweet corn. The so-called Sweet Gene hybrids are similar in most respects to Sugary Enhanced (se) types.

Super Sweets or Extra Sweets have a shrunken (sh) gene, a name that describes the light-weight, wrinkled seed of this group. This gene raises original levels of complex sugars even further, again extending their flavor by slowing conversion to simpler sugars and finally to starch. Moisture is also retained in this type and shelf life is remarkably long. There will usually be more seed per lb. in the (sh) types due to low seed density but growers should wait for ideal conditions (soil temperatures of at least 60-65 F and ample moisture) before planting. Shrunken (sh) corns should be isolated from all other types of corn in order to maintain their eating quality.

"Isolation" as used above can either mean at least 250 ft. apart, separated by an effective wind break, or 10 to 14 days difference in maturity because corn is wind pollinated.

Culture: Sweet corn prefers well-drained soils with a pH of 6.0-6.8 and a 2-1-1 or a 1-1-1 fertilizer ratio. Part or all of your first planting can be covered with clear plastic for a quicker start, slitting the plastic to allow seedling emergence when really warm weather arrives. At least 1 week of maturity will be gained this way. Corn should be planted in blocks to achieve complete pollination and varieties of the same genetic class and kernel color can be planted beside each other.

Varieties

The varieties listed are suited to West Virginia conditions. The best quality and highest production will be obtained from plantings of varieties of the main season and late group. Most gardeners, however, and some commercial growers will want to plant a limited amount of the early group since by doing so they can add about 10 days to the beginning of the sweet corn eating season.

A. Early
Sundance (su) yellow
Precocious (se) yellow
Bodacious (se) yellow
Seneca Starshine (se) white
Quick Silver (su) white
Quickie (se) bicolor
B. Main Season
Honey & Cream (su) bicolor
Bellringer (su) yellow
Super Sweet (sh) yellow
Silverado (se) white
Alpine (se) white
C. Late
Kandy Korn (se) yellow
Illini Xtra-sweet (sh) yellow
Silver Queen (su) white
Seneca Dancer (se) bicolor

Fertilization

Always use manure or compost if available but in addition, fertilize with a commercial fertilizer such as 10-10-10. The home gardener should follow a good garden fertilization program such as plowing down 25 pounds per 1,000 square feet and then broadcasting another 25 pounds per 1,000 square feet before disking or harrowing. A commercial grower using a planter with a fertilizer attachment should plow down about 1,000 pounds of 10-10-10 per acre and apply from 300 to 400 pounds in bands with the planter at planting time.

Side Dress

Unless the sweet corn ground has been heavily manured or a good legume turned under, it would be well to side dress with a nitrogen fertilizer such as ammonium nitrate or nitrate of soda. Make the application when the corn is about 16 to 18 inches high using about 200 pounds per acre (1 tablespoonful per hill). Make the application on top of the ground and about 3 inches out from the plant.

When to Plant

The home gardener and market gardener should plan to have a supply of fresh corn from about the middle of July until frost. This can be done by making a planting of both early and main season varieties and one of the late varieties the last of April or first of May and then each 10 days thereafter up until July 4. The planting made about May 15 will likely suffer less from corn earworm; therefore, this should be the largest planting for canning or freezing.

Thinning

With rows about 30 inches apart, thin the corn to one plant every 10 to 12 inches of row length. It is not advisable to sucker sweet corn.

Harvesting

Harvest mature corn during the cool part of the day. The corn will lose its sugar rapidly after picking if not kept cool (about 40F).

Pest Control

In West Virginia losses due to insects may start with early flea beetle invasions and be followed by European corn borer, corn earworm and Japanese beetle. If insect populations exceed acceptable levels, one or two insecticide applications should be made to control these pests.

Pest

When to Apply

Flea Beetles When first leaves begin to flatten out.
European Corn Borer Just as the first tassels begin to appear in the bottom of the whorl cup. Repeat in about 4 to 5 days.
Corn Earworm When about 10 percent of the ears begin to show silk. Repeat in about 3 to 4 days.

For current pest control recommendations contact your local county Extension office.