Because the blooms have both female and male organs, tomato plants are self-pollinating. Usually, a gentle breeze is all that is required to pollinate the tomato plant so that it will set fruit. Occasionally, nature goes awry and interferes with the process of pollination. Temperature extremes can prevent pollination. High humidity can prevent the male organ, (the stamen) from shedding the pollen, and extremely dry weather can prevent the pollen from adhering to the female organ (the stigma). When this happens, a helping hand will ensure that the tomato is pollinated, and can proceed with developing delicious tomatoes. To pollinate the tomato, use one of several simple methods.
Hand-pollinate the tomato plant in the middle of the day, after moisture has evaporated. Natural pollination takes place between 10 a.m. and 4 p.m. on dry, sunny days.
Jiggle the plant gently with your hands. Usually, gentle motion is enough to move the pollen from the stigma. You can also touch the tomato plant stem gently with a battery-operated toothbrush. The vibration is usually enough to release the pollen, much like the buzzing of a bumblebee.
Hand-pollinate the tomato blooms with an artist's paintbrush or a cotton swab, if gentle vibration doesn't work. Remember that a tomato bloom contains both male and female sex organs. Poke a tiny brush deep into the bloom, then rub the brush over the stigma, which is the tip of the bloom. Use a soft, dry brush so the pollen will be released, and won't stick to the brush.