Sweet Corn - Key Growing Information

An ear of developing sweet corn; a stalk at right shows male flowers with anthers and pollen.


SCIENTIFIC NAME: Zea mays
CULTURE: Planting in cold soil risks poor germination. Plant untreated seeds when soil is warm, at least 65°F (18°C). Plant treated seed when soil temperature is at least 60°F (16°C). Only treated seeds of good cold-germinating varieties may be sown in 55°F (13°C) soil and only if warmer weather is anticipated. Floating row covers may be used on early plantings to help moderate soil temperature.
PLANTING: Extensive crossing of super sweet varieties with non-super sweet varieties will cause tough, starchy kernels in both types. If you plan to grow both super sweet and non-super sweet varieties, avoid cross-pollination using any one of the following three options: 1) Plant super sweet varieties at least 300 feet from non-super sweet varieties, or 2) Stagger plantings by a 12-day planting date difference and separate each planting by 25 feet, or 3) Plant varieties that will mature at least 12 days apart and separate each planting by 25 feet. Sow 3/4–1" deep, 6–7" apart (or 2 seeds every 9", thinning to 1 plant), rows 30–36" apart. Increase this rate for untreated seeds. Arrange in blocks of at least 4 rows for proper pollination, which is needed for well-filled ears. Successive plantings can be made through early summer; most growers prefer to extend the sweet corn season by planting a few varieties of different maturities.
INSECT PESTS: Consult your local Extension office for Integrated Pest Management information. Reduce insect pests in the next corn crop by prompt plowing-in or removal and composting of cornstalks after harvest.
HARVEST: When kernels are full and "milky," generally indicated by a drying and browning of the ear silks. Record the date on which about half the plants show silk. Corn is ready to eat 18–24 days after ear silks first show; the warmer the weather, the sooner you can pick it.
DAYS TO MATURITY: Varies widely with weather conditions and planting dates. Use these figures to compare one variety to another, not to accurately predict maturity on a given day.
AVG. SEEDING RATE: 1M/500', 5M/2,500', 25M/12,500', 30M/acre at 2 seeds/ft. in rows 36" apart.
SEED SPECS: SEEDS/LB.: Avg. 2,700, su/se/synergistic type; Avg. 2,900 super sweet.
PACKET: 150 seeds, sows 75' at 2 seeds/ft.
PLEASE SPECIFY: (1) treated with fungicide seed protectants (T), or (2) untreated seeds. We offer most varieties untreated for organic growers. All fungicide treated corn seeds are polymer-coated after treatment to reduce rubbing off or dusting of the treatment.