The spring and summer of 2013 have not been kind to tomato lovers. First, there was the late frost May 22, 2013- the temperature went down to 28˚ F. I had about 16 tomato plants in the ground that day and lost 12 of them. So, I replanted tomatoes around May 25. The ones that didn't freeze were definitely stunted thanks to the cold weather.
On July 1, we experienced a record high temperature of 109˚F, and the average daily high temperature in July was 97°F. That is WAY TOO hot for tomatoes trying to blossom and set fruit.

So, now in August I have some nice green tomato plants with about 4 tomatoes per plant. Some of the indeterminate tomatoes (meaning their growth will continue until killed off by frost) are 6-7 feet high, but only have a few fruits hanging from their stems. Normally, these plants would be full of green tomatoes, their branches weighted down by heavy fruits. The heat in July has reduced the number of blossoms that were fertilized and so I have few tomatoes. The study,

    Tolerance of Tomato Cultivars and Selected
    Germplasm to Heat Stress

from the Journal of American Society of Horticulture Science, 1991, says that high temperatures will affect flowering and fruit set where temperatures reach, even for a short duration, above 100˚. Not only is fruit set affected but the heat also caused fruit abnormalities like cracking, blossom-end rot, watery tissue and small fruits. I am seeing this as well in the roma tomatoes. I planted a beautiful grafted roma tomato and now, the tomatoes are turning red and they are very small. Just larger than a ping pong ball! Normally, I would have tomatoes the size of a baseball. Plus, I have thrown away several of the small tomatoes because they had blossom-rot.

The good news is, now the average temperatures have gone down slightly and the tomatoes are blooming and the fruit is setting. Now, will the frost hold off long enough for these new tomatoes to ripen. It takes about 60 days for a tomato blossom to develop into a red tomato. This is August 12, sixty days from now will be October 12. There is a chance we could get some tomatoes for canning after all. The heart of a gardener is always optimistic!

Check out this website to see photos journaling the number of days from tomato blossom to ripe red tomato.