Pollination is the transfer of pollen from the male part of the flower to the female part of a flower. Pollination is of little significance to gardeners when they are growing vegetables for their foliage or roots.

Pollination becomes important when we grow vegetables for their seeds, fruit, or seed pods. Without pollination the seeds and fruit will not develop. Most plants have male and female flowers parts on the same flower and are easily pollinated by wind or insects.

One cause of poor fruit set is too much nitrogen, which can result in mostly vegetative growth. This is especially true with tomatoes, peppers, and cucumbers.

Too much shade or not enough light is another cause of poor fruit set. Most fruiting vegetables do best in full sun all day --- they need at least 6 to 8 hours of sunlight.

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.

Another group of plants, vine crops such as cucumbers, squash, pumpkins, cantaloupes, and watermelons have separate male and female flowers. To produce fruit, pollen from the male bloom must be transferred to the female bloom. Insects, mostly bumble bees and honey bees 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. Its 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. Two different cultivars of pumpkin can cross-pollinate, but the fruit would be not affected. However, if you saved and plant seeds from these cross-pollinated pumpkins you might get fruits of many different shapes, sizes, and colors. Cucumbers and squash will not cross pollinate each other - there is no effect on flavor when they are grown next to each other.

Corn is the one major exception to the rule. When a yellow and white cultivar that flower at the same time are planted near each other the resulting kernels will be mixed yellow and white. When a supersweet type corn is planted near a traditional corn cultivar, it will not develop its sweet flavor. Pop corn will not pop if it has been pollinated by sweet corn or field corn.

Consumer Horticulture | Quick Reference

© Erv Evans, Consumer Horticulturalist
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