Pollination of tomatoes

Luckily, tomates are self pollinating. The pollen is inside the flower, and when it is time to burst open some of it sticks to the end of the stigma, which is also inside the flower. I hope the following explains it simply enough.

Fertilization takes place in the reproductive organs of the flower. The female organs comprised of stigma, style and ovary, collectively are called the pistil. The male organs consist of the anther and filament and
are collectively called the stamen.

The tomato flowers of most varieties are self pollinating. The pollen from the anther is transferred to the stigma of the same flower. Tomato flowers will be cross pollinated occasionally. When this occurs the pollinator is usually the bumble bee. 

So what can we do to help pollination you might ask? Well, obviously the right growing conditions such as heat, light, water and nutrients will help to produce healthy flowers full of pollen.
As we cannot determine when the pollen is ready to burst open but when it does, some must get attached to the stigma. Any movement at this time will help, be it manually or like in nature, by the wind or bees.

By using various ways you can force the pollen to burst open, here are a few ways. But remeber most of these techniques are used by commercial grower who need to get every tomato set on every truss in the early part of the season, when prices for their crop is a lot highter than later in the year. Most amateur growers will just let nature take its course.
Commercial growers have developed a few techniques. One is a wind blower to shake the flowers, which to be honest I have never used. The other is a vibrating stick, usually made from a door bell with the bells removed, and the prong that is used to ring the bell is placed against the top unset trusses to vibrate them.

An average worker looks after 5000 plants and they vibrate all these plants about twice a week in the early part of the season to help fruit setting when they have a lower work load not having to pick or trim.

This has two benefits, firstly you can shake the trusses with the water spray and secondly, you cool the plants down in hot weather and add humidity. The only problem with this is that if the plants do not dry out by night fall and there is too much humidity in the greenhouse, then you are more likely to get diseases.
I do tend to spray my tomatoes a few times a day on really hot days though.

It sounds simple and it is, just shake the crop wires while you are working in or near the greenhouse and you are aiding pollination and its a lot quicker than the tickling stick!

Some flowers will produce tiny tomatoes, but if they have not devoloped in the right conditions, then they will not swell. This is usually down to low temperatures in the early part of the season.