The key to growing great sweet corn is providing rich, amended soil, sufficient moisture and fertilizer, and planting in block rows for good pollination.
When selecting corn seeds, you might be intrigued by the many varieties. Three genes control corn sweetness – Sugary (su), Sugary Enhancer (se) and Shrunken-2 (sh) – and these code letters are included on the packages.
Corn needs warm air and soil temperatures to germinate and grow properly and should be planted when the soil temperature is at least 50 degrees to ensure good seed germination. Super sweet (sh) varieties need even warmer soil temperatures, often closer to 60 degrees. Garden soil that has been amended with aged manure or compost and nitrogen fertilizer will help give the plants a good start.
Corn is wind pollinated and should be planted in blocks rather than single long rows. Plant two corn seeds an inch deep in each hole, spacing the holes 12 to 15 inches apart. Plant in rows spaced 30 to 36 inches apart, planting several rows together to form a row block. After germination, thin the corn to one plant from each hole.
Adequate soil moisture is crucial for plants to form acorns, silks and ears; the soil around the corn should not become too dry during the growing season. Uneven watering can retard plant growth, affecting the size and development of the ear. Fertilize the corn around the first week of July and control weeds.
Two cobs usually develop on a corn plant; the larger one is approaching the top. Harvest after the silk is dry and brown and the husk is still green, or when the kernels are full and pressure from your fingernail produces a milky liquid. Choose early in the morning for best flavor.
Growing sweet corn presents two common but manageable challenges. During harvest, you might find damage to the top of the ear from corn earworms. Less often, you might find firm, tumor-like growths on the leaves, stems, ears, and acorns. It is common corn smut, a fungal disease.
Here are two resources to guide you in this regard:
https://planttalk.colostate.edu/topics/insects-diseases/1468-corn-earworm/
https://extension.usu.edu/vegetableguide/sweet-corn/corn-smut
