Extreme temperatures can reduce fruit set. If temperatures during flowering are below 55 degrees or above 90 degrees, the pollen grains of many warm-season vegetables are damaged and become unable to cause pollination. To produce fruit, pollen from the male bloom must be transferred to the female bloom. Insects, mostly bumblebees and honeybees, transfer the pollen. Unless the plant is actively producing both male and female bloom or if insects are not working the bloom, pollination and fruit development will not occur.
Corn plants produce a female flower, the silks, and a male flower, the tassel.
Pollen falls on or is blown by wind to the silk and corn kernels begin to develop. When corn is planted in a single row, inadequate amounts of pollen may reach the silk and poor kernel development results. It's best to plant sweet corn in three or more short rows rather than a single long row. Many gardeners worry about planting certain crops near one another for fear that insects or wind might deposit foreign pollen on a given vegetable and produce off-flavors or shapes. However, if we saved and planted seeds from these cross-pollinated pumpkins we might get fruits of many different shapes, sizes, and colors.