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Sweet Corn Seeds

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When sweet corn season rolls around, customers look for the best eating quality at local roadside stands and farmers’ markets. May and June are months for planting sweet corn seeds to meet the required conditions for growing. Corn seeds should be planted in a spot that receives full sun, in well-draining soil. Plant seeds approximately one inch deep, spaced about 9-12" apart in each row in soil with a temperature of about 60 degrees or above. You can check soil temperature with a soil thermometer and sunlight, soil PH, moisture, and fertility levels can be verified with an electronic soil analyzer or soil testing kit. Sweet corn requires frequent watering to produce full, healthy ears. Once the tassels appear, you should provide at least one inch of water per week. Make sure the soil doesn’t dry out between waterings. If your area is experiencing particularly hot and dry weather, make sure to water more frequently.

Sweet corn has evolved over the last twenty years, turning into superior varieties with high eating quality and disease resistance. The hybrids of today are far superior in eating quality compared to heirlooms, open-pollinated and older sweet corn hybrid varieties.

New hybrids are tested for several sweet corn diseases each year to ensure intermediate resistance or resistance. The most promising experimental are grown in trials throughout the country to test their adaptability before they are named and offered for sale. Throughout the breeding and testing period, constant attention remains on the most desirable characteristics featured in Harris' sweet corns; seed vigor in the cold soils, disease resistance levels, dark green flag leaves, husk and ear appearance and eating quality.

There are five basic genetic types of sweet corn we offer:
• normal sugary (su)
• sugary enhanced (se)
• synergistic se (sy)
• supersweet (sh)
• augmented supersweet (shA)


Discovery and development of new genes for eating quality in sweet corn are ongoing. The supersweet gene is the drastic mutation of field corn known by breeders as "shrunken" or shortened to "sh3". This recessive gene results in the production and retention of unusually high natural sugars and is commonly called "supersweet" or "extra-sweet" corn. These varieties are very sweet and unusually crisp textured to eat, though recent developments have yielded varieties with more tender textures. These varieties are known as “augmented supersweets”. The high sugars that are produced tend to accumulate in the kernels because the sh3 gene blocks their conversion to starch. The retention of sugars and the lack of starch continue and prevail in the dried corn seeds used for planting. It is this lack of starch that makes the seeds lightweight, wrinkled and shrunken. The physical stresses of shrinking leads to more cracks and splits in the seed coats of supersweets than with other corn varieties.


The seeds of supersweet types have less food reserve than others, thus storing less energy for germination, emergence, root and shoot growth. The seed is brittle and prone to cracking and splitting. When the seed coat breaks, nutrients can leak out, attracting microorganisms. Some of the organisms are pathogenic fungi that cause disease by penetrating maturing seeds on field ears. Soil-borne fungi can also grow rapidly in the leach. The the result can be seed rot, damping off, die back, whip-like plants and plants that don’t yield. Combat these risks with a broad-spectrum seed treatment, combining several fungicides approved for this purpose. There is no single fungicide available that controls all vulnerabilities.


• Cross-pollination between supersweets and other genetic classes will turn corn kernels tough and starchy. This effect works both ways. Since corn is wind-pollinated, the supersweets should be isolated at least 250ft from all other non-sh3 corn (field, su, se, sb, sy, pop, ornamental etc.), use natural wind barriers and/or plant with 10-14 days maturity difference between varieties. Cross-pollination only effects two supersweet varieties if they have different kernel colors.
• Most of corn seeds prefer soil temperatures of 60°F or higher. Choose cold-tolerant varieties for early planting or cover the planted seed to warm the soil. Plant supersweets on south-sloping fields that tend to be warmer.
• A loose, well-drained seed bed promotes germination as long as it's not overworked and dry. Avoid soil compaction and crusting. Soil moisture should be present at planting time. Plant as shallow as moisture will allow (1-1.5" deep is best). Avoid irrigating with cold water, as it causes seed cell damage. Once the tassels appear, you should provide at least one inch of water per week. Make sure the soil doesn’t dry out between waterings. If your area is experiencing particularly hot and dry weather, make sure to water more frequently.
Fertility Rate
• A balanced fertility rate of 2-1-1 (N-P-K) and pH of 6.5 is best for sweet corn.
Pest Control
• Insecticides are effective when applied at planting to control wire-worms, seed corn maggot, army worm, cut worm, flea beetle, etc. Birds and rodents are attracted to germinating supersweets- use animal control techniques to protect crops.
• Avoid handling and storage of supersweets and store seeds in a cool, dry spot for maximum germination. Sweet corn seeds age slowly and safely if stored properly. Slow planting speeds of 3-4 MPH produce better singulation of the lightweight seeds.

Average Seed Count: 250-300 per packet; 2,500 - 4,200/Lb.

Sweet Corn Growing Guide

Bicolor Sweet Corn

White Sweet Corn

Yellow Sweet Corn

SSW® Sweet Corn

Sweet Corn Collections


Harris Seeds began operation in 1879 from the efforts of Joseph Harris, who was successful in selecting only the highest quality vegetables and grains. The company gained popularity because of his basic business philosophy: "Offer customers a quality product at a fair price and they will return." READ MORE



Harris Seeds of Rochester New York
355 Paul Rd.
P.O. Box 24966
Rochester, NY 14624

Phone: (800) 544-7938
FAX: (877) 892-9197

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