First I should say that you don't prune all tomato plants. Before you start, you need to know if your tomato is a determinate or indeterminate variety. You will only want to prune an indeterminate variety, because they are the type of tomato that will keep growing and producing new flowers and tomatoes all season long. If your tomato is determinate, which many tomatoes label, 'patio,' or 'tiny' often are, you do not want to prune it.If your tomatoes are indeterminate, you will want to prune tomato plants for several reasons.
- Healthier Plants - Tomatoes are susceptible to all kinds of diseases and fungi, by keeping your tomatoes pruned, you increase the air circulation around the plants and reduce the chances of sickeness.
- More Tomatoes - Even though it is contrary to what one would expect, if you keep your tomatoes pruned you will get more fruit. While I haven't done a scientific study on this, it is common wisdom, practiced by the best gardeners I know.
- Tamer Plants - Even my well-pruned tomatoes can get wild and wooly when they are in full swing. This can invite staking or trellis failure and fallen over tomatoes are not pretty, or healthy.