"Self Pollinating" and Tomato Growing Mythology
Long ago, a group of monks got into a discussion of horses teeth. How many did a horse have? All the ancient writings were consulted, and the discussion became more and more heated. Finally a young monk suggested they look in the horse's mouth. One and all turned on this impertinent, irreverent monk and they literally threw him out of the monastery.
At risk of being thrown out of tomato groups, I will try to inject some common sense into the tomato pollination discussion. It's funny how often it's said that tomatoes self pollinate, but always in the context of ways to help them self pollinate, or reasons why they didn't self pollinate. Oxymoronish isn't it?
The best pollinator for tomatoes is the original, a bee which "sonicated" at the resonant frequency of the flower. Sonication, also called buzz pollination is when the bee vibrates its wing muscles but doesn't fly; it just hangs on.
The reason is that tomato pollen is not in the exterior of the anthers like most flowers, rather it is produced internally and then released thru pores in the anther. Motion is required to release the pollen, and the greatest quantity is released by sonication of the correct frequency. However other bees with different frequency, or even shaking by wind will release some pollen.
There are a couple problems: one is that the natural pollinator (a wild bee) didn't travel with the tomato as it was spread throughout the world. The other is that the flower is not very attractive to other bees, and when bee populations are low the tomato generally gets ignored. Bumblebees are the most often seen on tomatoes, though honeybees, when hungry enough will also work them, as will some solitary bees.
Did you ever watch a bumblebee work a tomato blossom? When it does, it pulls the flower down into a vertical position, puts its fat belly against the stigma, and buzzes. The pollen that is released, now will fall by gravity (since the flower is now tilting down) directly to the bee's fuzzy (and statically charged) belly, which is rubbing against the sticky stigma as it vibrates. Tomatoes are self fertile, but the pollen can come from any other tomato that the bee has visited, a bane for seed growers who want to keep varieties pure, but lovely for the gardener who wants fruit.
The size of the fruit is dependent on the number of ovules fertilized, up to the 100% mark. In other words, the more seeds, the meatier the 'mater. So we want to get pollination as full as possible. This is the reason the bee is best, it delivers the most grains of pollen, exactly where it is needed, on the sticky surface of the stigma.
When shaking is done by hand, think about mimicking the natural resonances of sonicating bees. Shaking should not be violent, just as close to the right frequency as possible. Electric vibrators were long used in greenhouses for tomatoes, but have been replaced, as bumblebees are found to be far more efficient. Using an artist brush with tomatoes is very inefficient because the pollen is not on the surface.
Yup, tomatoes are self fertile, but self pollinating?...only when conditions are ideal...they often need help. "Self pollinating" is one of the myths of tomato growers.
Tomato Pollination Pictures