Tomato Plants Not Fruiting as Expected?
Many folks are experiencing trouble with fruit set on their tomatoes this spring, at least in Texas. There are a few contributing factors to this problem this year, some out of your control, some not.
What I'm noticing is that anyone that planted their tomato transplants after March 15th are the ones having the most problems. We've had a very cool wet spring this year and temperatures have not been great for flower/fruit production. Also, we went from 50F days straight into 90 degree days...also not condusive for fruit set. Folks that got their plants in the ground before March 15th had more time for plants to develop on schedule. This is why I always encourage gardeners to get their tomatoes in the ground BY March 15th. Waiting for "bad" weather to pass to plant your tomatoes is almost always a recipe for minimal fruit set. Plant your tomatoes early and keep some frost cloth on hand to protect them from frosts.
Also, I've spoken to several people that continued fertilizing their tomatoes through this cool spring, even though flower/fruit production had not set in. Too much Nitrogen before flowering/fruit set will only continue to encourage lots of green leafy growth...not flowers and fruit. You should fertilize your tomatoes at planting time and then wait until you have baby fruits setting on the plant. THEN start fertilizing about every two weeks through harvest.
Fruit set this year, due to weather conditions, will also vary by variety. Some varieties that are more temperature sensitive won't yield as much this time around. Troopers like 'Sapho', however, should still perform pretty well.
You can reference this older post of mine for more specifics on temperature and fruit set for tomatoes.