Why doesn't my tomato plant have tomatos?

Answer 1

Conditions Are too Good
The most common reason why an apparently healthy tomato plant has no fruit, when growing outdoors, is that its soil is too fertile. Tomato plants go to seed when they are stressed by slightly infertile conditions...liken this to cool-weather plants that must be protected from heat, lest THEY go to seed.
Since, unlike lettuce and broccoli, we actually want tomatoes to go to seed (bear fruit), we have to take care in these ways:

• Be careful not to give them fertilizer with much nitrogen.
• It's also possible for soil to have too much nitrogen already.
• A third source of over-fertility is nearby legumes: Bean, pea, and clover plants host a bacteria that fixes nitrogen into the soil, and are good for planting near cucurbits (cucumbers, squash, and melons), brassica (broccoli, cabbage), and corn, but should never be grown near tomatoes or peppers.

The Plant is too Still
If the obviously healthy plant plant is actually blooming, but not setting fruit, then the problem is likely to not be overly fertile soil, but overly still air.

If the air is extremely still (no breeze) for weeks at a time, or you are growing tomatoes indoors, you can get blooms that do not "set" into fruit. This is because they are not getting pollinated. Tomatoes are self-pollinating, but they need at least a light breeze, or American-native pollinators to disturb them.

You can easily fix this, simply by gently shaking the entire plant (very gently) every day or two. Animals like birds visiting the plants can have a similar effect.

Note that honeybees are an invasive species from the Old World, while tomato plants are native to the Americas; No plants native to the Americas need, or even can use, honeybees for pollination. Pumpkins need squash bees, tomatoes air-pollinate, corn is pollinated by birds, wind, and large American insects, et cetera. Encourage native pollinators in your garden, by including "companion plants" that will attract them, like umbellifers (queen anne's lace and parsley, for example). They are old world plants, but their flowers attract few honeybees, and are the right size for many native pollinators.