Few Tomatoes

Question:

Why are my tomato plants producing so few tomatoes?

Minnesota Master Gardeners say:

There are many reasons why tomatoes won't bear fruit. You will have to do some detective work to figure out what the reason is. The first question you should ask is: Is the tomato blossoming?

If it is not, then the possibilities are: too much nitrogen (which promotes leaf growth at the expense of blossoms and fruit) or shade (tomatoes need 6-8 hours direct sun per day).

If the tomato is blossoming, but the blossoms are falling off, then the possibilities are: extreme temperatures (above 85 degrees or below 55 degrees for daytime highs), not enough water, and lack of pollinators (not enough bees).

For further reading:
Where have all the flowers gone? http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-July1502.html#flowers