Growing Home GardenSweet Corn

Robert R. Westerfield, Extension Horticulturist

Nothing can compare to the fresh, sweet, crisptaste of homegrown sweet corn that is pickedand eaten on the same day. Sweet corn is cer-tainly a favorite crop among home gardenersand, with the many varieties now available, thereis one to suit every taste and need. Sweet corn isnot difficult to grow and, by following the culturalguidelines provided in this publication, you toocan enjoy this sweet delicacy.

TypesSweet corn may be divided into three distinct

types according to genetic background: normalsugary (su), sugary enhanced (se) and supersweet

2(sh ). There are also varieties now containing acombination of either two or all three of thesegenes, exhibiting qualities of each.

Standard sweet corn varieties contain a “sug-ary (su) gene” that is responsible for the sweet-ness and creamy texture of the kernels. Su’s arebest suited to being picked, husked and eatenwithin a very short time.

Sugary enhanced hybrids contain the sugaryenhancer (se) gene that significantly raises thesugar content above standard varieties whileretaining the tenderness and creamy texture ofstandard varieties. No isolation from standardvarieties is necessary.

2Supersweet hybrids contain the shrunken (sh )gene, which delays the conversion of sugar tostarch, allowing them to stay sweet longer thansu varieties. The kernels of the supersweet varie-ties have a crispy, tough-skinned texture and

contain low amounts of the water-soluble poly-saccharides that impart the creamy texture and“corn” flavor to other sweet corn varieties. Al-though the lack of creamy texture is not especi-ally noticeable in fresh corn on the cob, it affectsthe quality of frozen and canned corn, as doesthe toughness of the seed coat. Unless corn mustbe stored, shipped or mechanically harvested,

2se’s are superior in eating quality to sh ’s.2Supersweets (sh ) should be isolated from any

other type of corn tasseling at the same time toensure sweetness and tenderness. Their pollen isweak and easily supplanted by other types, whichcauses the kernel to revert to a form with thetoughness and starchiness of field corn. Becausecorn is wind-pollinated, this isolation distanceshould be 500 feet or more, especially down-wind.

Many new varieties contain two or all threetypes of genes. These may be called by severaldifferent terms including mixed gene, multi-gene,superior eating quality, sweet breeds and extratender among other names. All of these should

2be isolated in the same manner as the shvarieties.

Soil PreparationSweet corn thrives best in loamy, well-drained

soils but will tolerate a wide range of soil types.Optimum pH ranges from 6.0 to 6.5.

Till the soil to a depth of 6 to 8 inches using aspade, plow or rototiller. Avoid tilling the soilwhile it is too wet or large clods may be formed.

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Planting

Sweet corn is a warm-season vegetablerequiring soil temperatures between 60-90degrees F. Avoid planting seed in cool soils. Waituntil at least two weeks after the last averagekilling frost before planting. If planted too early,weak stands, stunted growth or frost-killedseedlings may result. The newer, sweeter vari-eties are even more sensitive to cool, wet soilsand may not perform well in these conditions.

Plant corn in an area that receives at least 8 to10 hours of sunlight. It is beneficial to plant near awater source for needed irrigation.

Plant seed approximately 1 inch deep in rows3 feet apart with 8 to 12 inches between eachseed in the row. A hand pushed mechanicalplanter can make seeding much easier for largerstands of corn. (Figure 1)

Corn is wind pollinated, so plant four or moreshort rows of sweet corn side-by-side instead ofone long row. This will aid in good pollinationand ear development. (Figure 2)

2Plant sh and multi-gene varieties 400 yardsaway from standard varieties, or plant so maturitydates are 1 month apart to avoid cross pollina-tion.

Fertilizing

A soil test through the local county extensionoffice is always the best way to determine thelime and fertilizer needs. If lime is required, it canbe tilled into the ground during soil preparationbut is most effective when applied 2 to 3 monthsprior to planting.

If a soil test is not done, a general guideline isto apply 6 pounds of 10-10-10 per 100 linearrow feet before planting. Sidedress two to threetimes during the growing season with ammon-ium nitrate (34-0-0) at a rate of 1 pound per 100feet of row. More frequent sidedressing may berequired on sandy soils or when excessive rainoccurs. Sidedressing involves digging a shallowtrench on one side of the row, near the plant, andapplying fertilizer. It is then covered with soil.(Figures 3 and 4, page 3)

Watering

Water is vital to ensure a good stand of corn.Corn requires a minimum of 1 inch of water perweek for normal development. The most criticalperiods for water are during pollination and dur-ing final ear filling.

Water sufficiently to moisten the soil to adepth of 6 inches. Irrigate in the early morning orearly evening to allow foliage to dry before dark.Soaker hoses placed along-side of rows are anexcellent way to irrigate corn and conserve water.

Maintaining

Keep rows clean and free from weeds. Light,shallow tilling between rows can be done, buttake care not to get too close to the root systemof the corn. After cultivating with a tiller or hoe,mound soil 2-3 inches up around the base of theplants to support stalks from wind damage.

Figure 1. Hand pushed mechanical planter. Figure 2. Plant several short rows.

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On small stands of corn, where it is practical,place organic mulches around plants to helpconserve moisture and control weeds.

Maturity and Harvest

Sweet corn matures in 60 to 100 days, de-pending on the variety. For a continuous harvest,plant early, mid and late season varieties or makesuccessive two-week plantings of the samevariety.

Sweet corn should be ready for harvest about20 days after the appearance of the first silkstrands. Sweet corn is picked during the “milkstage,” when the kernels are fully formed but notcompletely mature. Sweet corn is ready to har-vest when the silks become dry and brown andthe kernels are smooth, plump and pop openwhen punctured with a thumbnail. Not every earin the row will be ready at the same time andthey may mature several days apart.

After picking, cook and eat corn right away orstore it in cool temperatures, such as in a refrig-erator, as soon as possible. It can then be canned,frozen or eaten fresh within a few days. Keepingthe corn cool is the key to better flavor as hightemperatures will convert the sugar in the kernelsto starch, giving it a bland taste. Although manynew varieties have extended storage quality,most lose 50 percent of their flavor within 12 to18 hours of picking if left unrefrigerated.

Problems

Common cultural problems of sweet corninclude poor kernel development caused by dry

weather during silking, planting too close, poorfertility, too few rows in a block causing poorpollination, and lodging (falling over) from toomuch nitrogen and/or wind damage.

High temperature and poor water manage-ment during the tasseling stage can cause poorpollination and fewer kernels on the ears. Insectssuch as Japanese beetles can also affect kernelpollination by eating the silk.

Common insect problems that will be encoun-tered in sweet corn include corn earworm, aphidsand flea beetles. Cutworms, seed-corn maggots,Southern corn rootworm, wireworms, fall army-worm, European corn borers and Japanesebeetles may be encountered as pests of sweetcorn.

Check with your local county extension agentfor recommendations for controlling and prevent-ing these pests.

Sweet corn is seldom seriously damaged bydiseases in the home garden. The followingproper cultural practices can reduce or preventmany potential disease problems:

• Obtain seed from a reputable seed source anduse fungicide, pre-treated seed to reduceproblems with damping-off.

• Plant when the soil temperature is above 55degrees F to reduce most seedling rots.

• Keep the garden free of nearby weeds, whichcan harbor viruses.

• Remove corn smut-infested ears promptlyfrom the stalks and garden area.

• Remove plant debris after harvest to reducediseases that may over-winter in the old stalks.

Figure 3. Figure 4.

Circular 905 Reviewed December 2012

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. Cooperative Extension, the Uni-versity of Georgia College of Agricultural and Environmental Sciences, offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, gender or disability.