Sweet corn, a warm season crop, is one of the most popular vegetables. An excellent summer treat, sweet corn may also be canned or frozen for year round use.
When purchasing sweet corn, home gardeners can select varieties that produce yellow, white, or bicolored ears. New novelty varieties produce multi-colored ( Indian Summer') or reddish kernels ( Ruby Queen'). While there are numerous sweet corn varieties, there are three main types of sweet corn. Standard (su), sugar-enhanced (se), and shrunken-2 (sh2) types vary in sweetness, keeping quality after harvest, and cold soil vigor.
Standard sweet corn varieties have been grown for many years. These varieties possess the traditional sweet corn flavor and texture. (Sweet corn differs from field corn by a single gene called the sugary or su gene.) Unfortunately, the ears of standard sweet corn varieties retain their quality for only 1 or 2 days. Also, standard varieties don't store well once harvested. Suggested standard sweet corn varieties for home gardens in Iowa include Seneca Horizon' (yellow) and Silver Queen' (white).
The sugar-enhanced varieties produce ears with sweet, tender kernels. The soft kernel pericarps make the corn tender and easy to chew. The harvest and storage periods of se types are slightly longer than the standard sweet corn varieties. They also have a higher sugar content. Suggested sugar-enhanced varieties for home gardens include Bodacious' (yellow), Incredible' (yellow), Legend' (yellow), Precious Gem' (bicolor), and Silver King' (white).
The common name of the shrunken-2 varieties is derived from the shrunken or wrinkled appearance of the dried kernels. The sh2 varieties are also referred to as super sweets. Shrunken- 2 varieties possess the longest harvest and storage periods and have the highest sugar content. However, sh2 varieties do have some disadvantages. The seed coats on this type are fairly thick, giving the kernels a tougher or crunchy texture. Yields of super sweets are generally lower than standard sweet corn varieties. They are also slow to germinate and have reduced seedling vigor. Suggested sh2 varieties include Candy Store' (bicolor), Challenger' (yellow), Confection' (bicolor), Honey N Pearl' (bicolor), How Sweet It Is' (white), Illini Gold' (yellow), Northern Xtra Sweet' (yellow), and Phenomenal' (bicolor).
Sweet corn performs best in fertile, well-drained soils in full sun. Standard sweet corn varieties may be planted in late April in central Iowa. It's generally recommended that se varieties be planted 1 week later than standard sweet corn varieties. The seeds of sh2 varieties germinate poorly when soil temperatures are below 65ÃƒÂ»F. As a result, shrunken-2 varieties should not be planted until mid-May in central Iowa. For a continuous supply of sweet corn, plant early, mid- season, and late varieties or plant every 2 or 3 weeks. The last practical date for planting early varieties is July 1.
Sow seed at a depth of 1 inch in heavy soils. In light sandy soils, the planting depth may be 2 inches. Space the seeds 8 to 12 inches apart in rows 2 1/2 to 3 feet apart. Sweet corn may also be planted in "hills." Sow 4 to 5 seeds per hill with approximately 3 inches between seeds. Hills should be spaced 2 1/2 feet apart with 2 1/2 to 3 feet between rows.
Sweet corn is wind pollinated. To insure good pollination and ear development, plant several short rows or blocks rather than 1 or 2 long rows. Poor pollination results in poorly filled ears.
Since different types of corn can cross-pollinate and contaminate one another, they should be isolated from one another. All sweet corn types should be isolated from field corn, popcorn, and ornamental corn. Shrunken-2 varieties must also be isolated from sugar-enhanced and standard sweet corn varieties. Cross-pollination between the sh2 and se or su varieties will destroy the quality of both. It is not essential to isolate sugar-enhanced varieties from standard sweet corn.
Isolation can be achieved by planting the different types at least 250 feet from one another and by avoiding prevailing winds. Another method is to stagger planting dates or to select varieties that mature at different times. A minimum of 14 days should separate the tasseling time of the different types.
This article originally appeared in the April 20, 2001 issue, pp. 42-43.