Tomato plants are just like any other fruit or vegetable--they need to be trimmed back regularly. The difference is that a tomato plant needs to have the extra leaves trimmed off even if they are healthy to help direct all nutrient growth to the fruit. There are two types of tomato plants: indeterminate and determinate. Indeterminate plants are best as vines and can grow up to 10 feet tall, while determinate plants are squat and bushy, not growing more than 3 to 4 feet tall. Each tomato variety requires you to cut back extra leaves with simple tools.
Sanitize your pruning shears with the rag soaked in rubbing alcohol. This step is important because dirty pruning shears can spread disease to the tomato plant, eventually killing it.
Trim back any dead leaves from the plant. If the whole branch is dead or broken, trim it off to the trunk.
Pinch off the tips of the branches during the growing season to promote fruit production and healthy, full growth. The tips are basically extra leaves from the tomato plant. To do this, trim off the last two sets of leaves from every branch.
Remove all leaves, suckers and small stems with the pruning shears each spring, before the first flowers set on the tomato branch. Trim back any leaves that are facing down. A well-pruned tomato plant should show all its leaves up toward the sun.