Pollination takes place when pollen from the stamen of a flower (the male sexual organ) comes into contact with the stigma (the female sexual organ). Pollination, required for vegetables to yield fruit, is ordinarily achieved by bees and other insects and sometimes by the wind. In cases where there are no bees or vegetables are grown indoors or gardeners are cultivating hybrid species, you can pollinate flowers of vegetable plants by hand.
The male stamen consists of a stalk with a tiny knob at the tip called an anther; the anther contains tiny sacs of pollen. The female stigma usually has a small bump at the bottom and contains a sticky substance to collect pollen. The bump is the female ovary. When the stigma receives pollen, the bump will swell and grow into a fruit. Flowers often produce fragrant nectar to lure bees and pollinating insects to the stigma.
Plants are said to have "perfect" flowers if each flower has both male and female parts. Vegetables with perfect flowers are self pollinating. Self-pollinating vegetables include eggplants, peas and tomatoes. Beans and chilies also have perfect flowers. The pollen in bean flowers is transferred before the flowers open. Self-pollinating flowers are pollinated manually by shaking the flowers gently or using a soft paintbrush to gently brush their insides.
Plants in the cucurbit family have separate male and female flowers; these vegetables include cucumbers, pumpkins, squash, cantaloupes and honeydews. Pollinating flowers of different sexes is similar to pollinating perfect flowers. The pollen from male anther is collected with a soft paintbrush or shaken into a container; it is then brushed or gently dusted on the female stigma.
Manual pollination of cucurbits begins with removing the petals from the male flowers to expose the anthers that contain the pollen. The anthers can be rubbed directly onto a female stigma. An artist's paintbrush can also be used to transfer the pollen. The male flowers commonly fall off the plant after the pollen has been transferred. A female flower that has been pollinated will remain on the vine so that the fertilized ovary will develop into a cucumber, squash or other member of the cucurbit family.
Corn is pollinated by the wind. The tassel at the top of young corn plant has male anthers containing pollen along its branches. Leaves and silks grow from nodes on the corn stalk; the silks are the female stigmas that collect pollen. Once the tassels appear, their anthers start shedding pollen with the morning sun. The tassels are shaken over a container to collect the pollen, a bright yellow powder. The pollen is spread on silks that are sometimes bagged to prevent contamination by other pollen from neighboring fields blowing in the wind.
When two varieties are cross-pollinated, the result is a hybrid. All vegetables have two Latin names. The first name is the genus; the second is the species. Plants of the same genus but different species usually will not cross. Zucchini (Cucurbita pepo) and Buttercup squash (Cucurbita maximuma) are both cucurbits, but they are different species; they will not cross. Zucchini may be crossed with yellowneck summer squash; both are Cucurbita pepo.