HO-98
Growing Sweet Corn
HOME YARD & GARDEN • COOPERATIVE EXTENSION SERVICE
DEPARTMENT OF HORTICULTURE • PURDUE UNIVERSITY  WEST LAFAYETTE, IN
B. Rosie Lerner and Michael N. Dana

Sweet corn is one of the favorite home garden vegetables. Improved hybrid cultivars are easy to grow. They yield well, taste sweeter, and store longer than old time cultivars. But sweet corn is best adapted to larger gardens since only one or two ears are produced per plant and several rows are recommended to ensure adequate pollination.
Sweet corn is available as yellow, white, or bicolored ear types. Cultivars vary in their days to maturity; they are classified as early, mid-, and late season. Late season cultivars generally are the best quality. Many of the new cultivars are higher in sugar content and retain their sweetness longer. See HO-101, Recommended Vegetable Varieties for Indiana for a current list of recommended cultivars.

Soil Preparation
Sweet corn thrives best in deep, naturally rich, easily worked soil. However, any well-drained soil is suitable. Sandy soils are best for early crops since sandy soils warm up faster in the spring than heavy soils. Sweet corn will adapt to a wide range of soil pH. However, optimum growth is obtained at pH 6.0 to 6.5.
Prepare the soil about 6 inches deep, using either a spade, plow, or rototiller. Break up the clods to insure good contact between the soil and the seed, then rake the soil to level the surface.

Fertilizer
In the absence of a soil test, apply 3 to 4 pounds of 12-12-12 or similar analysis fertilizer per 100 square feet to establish a basic fertility level. Side-dressing with a high nitrogen fertilizer late in the growing season is also advisable (see below). For an accurate recommendation of your soil’s fertilizer needs, have your soil tested before applying fertilizer. You may contact your local Cooperative Extension Office, or see HO-71, Soil Sampling for Homeowners.
Planting
Sweet corn is a warm season crop requiring a minimum soil temperature of 50° F (60-95° F is optimum) for seed germination. Seed should not be planted earlier than 10 days to 2 weeks after the average date of the last killing frost. See HO-186, Indiana Vegetable Planting Calendar, for recommended planting dates for your area. If planted too early, poor stands, retarded growth, or frost-killed seedlings may result. However, it may be worthwhile to risk the chance of frost in order to get an early crop.
Starting out with fresh purchased seed each year is advisable. Sweet corn seed is relatively short-lived (2 years), even under ideal storage conditions. Saving seed from last year’s hybrid crop is not recommended since seed from hybrid plants shows considerable variability and usually produces inferior plants and ears.
If poor germination does occur, don’t replant the “skips” or missing plants. The plants that develop from the replanted kernels will be crowded and shaded by the older plants and then yield poorly. Replants would not be ready for pollination at the same time as the original planting. If the stand is very poor, it is best to replant the entire area.
Plant the kernels 1 inch deep in heavy soils and no deeper than 2 inches in very light sandy soils. Space the rows 2 to 3 feet apart. Plant early cultivars 8 to 10 inches apart in the row and late cultivars 9 to 12 inches apart. Corn can also be planted in “hills” or mounds instead of rows; use 5 or 6 seeds per hill and then thin to 3 strong plants per hill. Space hills about 3 feet apart.
For a steady supply of sweet corn throughout the season, include early, midseason, and late cultivars in your initial planting. Successive plantings of mid - or late season cultivars about every two weeks will help stretch the harvest season.
Corn is wind pollinated, so plant four or more short rows of sweet corn side-by-side