Why do I have lots of leaves but no flowers on my tomato?

The plant is likely getting too much nitrogen, which triggers it to grow foliage, and not enough phosphorus, which favors flowering and fruiting. Choose a fertilizer that has a balanced ratio of the three major elements, such as 10-10-10, or where the middle number (phosphorus) is larger than the first number (nitrogen) such as 2-3-1. Tomatoes are heavy feeders and usually do need fertilizer unless your soil is very rich. But follow manufacturer's directions to avoid overdoing it.