Pollinating Tomatoes under HPS and MH Grow Lights

by Jerry Morse
(Vicksburg, MS USA 39180)

I have a Better Boy tomato that is growing under inside grow lights. It is blossoming now and has been for about 2 weeks. Will an oscillating fan cause it to pollinate, or do I have to pollinate manually? I have read the article about using an electric tooth brush to pollinate, but I am lazy, do not understand that technique and prefer the oscillating fan if it will do the trick.

Answer: While certain crops, like corn, are exclusively pollinated by the wind, tomatoes rely quite a bit on the action of bees for pollination. The difference between corn and tomatoes is that corn flowers open up to release their pollen, while tomatoes produce their pollen inside a protected part of the flower that does not open to release the pollen....these "pollen sacs" have only a very tiny hole from which pollen can escape.

Normally, the pollen has a very difficult time escaping. The pollen tends to cling to the inside wall of the pollen sac. Even when it is struck, as with the flick of a finger, only a little pollen comes out. However, when a bee lands on the tomato flower, the high frequency vibrations caused by the flapping of its wings prevents the pollen from clinging to the walls of the pollen sac.... the pollen begins to pour out of the pollen sac like sand through a time glass.

The reason an electric toothbrush is recommended is because it simulates the high frequency vibration, helping the tomato flower to release large quantities of pollen. A vibrator could be used also. Even this, however, is not enough to ensure lots of tomatoes (or to ensure you get large tomatoes). Once the pollen has left the tomato flower, it needs a way of getting onto the pistils of all the other tomato flowers.

The least productive way to do this would be to allow the natural air currents take the pollen where it will. You can increase the effectiveness of this method by increasing the air movement in the room while you are releasing the pollen (such as with an oscillating fan). However, if you want to guarantee large numbers of fat tomatoes on every plant, you either have to let the bees have access to your tomatoes (not an option in winter) or else you have to hand pollinate.

To pollinate by hand, you first need to collect some pollen.....the more the better (this is where the electric toothbrush comes in handy). Then, dip a very fine paint brush into the pollen and brush it over the pistils in the center of each tomato flower. I have read that each grain of pollen becomes a seed in the tomato, therefore more pollen equals fatter tomatoes. Direct contact, by bees or by paint brush, are the best ways to accomplish this.

If you do nothing and simply let nature take its course, you will still get a few tomatoes on each plant. On the other hand, considering all of the time and effort it takes to grow the tomatoes, it might be worth the extra step to ensure a bountiful harvest. For those who would like more information, visit my page on growing tomatoes.

And by the way, I would love to hear how things turn out when you're all finished!