Variety Selection

• Corn planted closely together does not cross-pollinate unless more than one cultivar develops tassels at the same time. To decrease cross-pollination, stagger planting times or select cultivars with different maturation dates. Allow 14 days between tassling times. Plant early, mid-season and late corn varieties to extend the growing season without cross-pollination. Early varieties include Earlivee and Seneca Horizon; Miracle and Bon Appetit are mid-season varieties; late-season varieties include Golden Cross, Bantam and Lochief. Bi-color corn is an intentional cross-pollination between yellow and white corn varieties.
  
  

Distance

• When planting corn varieties with similar tassel times, allow at least 250 feet between varieties to reduce cross-pollination. Less cross-pollination occurs when corn is not planted in the path of prevailing winds. Though not necessary for home gardeners, maintaining a distance of 700 feet between varieties completely eliminates any chance of cross-pollination.
  
  

Barriers

• Row covers -- lightweight fabric designed to allow sunlight and water in while providing protection to plants from insects and harsh weather -- reduce cross-pollination between corn varieties. This method necessitates manual pollination by the gardener, however. To pollinate corn manually, pollen grains from the tassel must come in contact with the silk at the nodes. Cut one tassel and wave it like a wand to make pollen grains land on the silk. Cover the silk completely to ensure adequate pollination. Other barrier methods include growing three sacrificial rows of corn on the border of each corn plot, to catch most of the pollen between plots.
  
  

Maturation Rates

• Environmental factors (including heat and drought) affect corn pollination rates. When temperatures exceed 95 degrees Fahrenheit and humidity levels are low, the quality of pollen decreases, and less silk is available to accept the pollen. High temperatures combined with drought reduce the number of days corn plants pollinate from eight to about two. Low soil fertility early in the development of corn plants may slow corn development and cause the plants to pollinate later than expected.