Tomatoes are grouped by growth habit. A tomato variety is classified as either determinate or indeterminate. Determinate tomatoes grow to about 4 or 5 feet tall, stop growing, and begin producing fruit. All fruit on a determinate tomato plant ripens within about 4 to 6 weeks. Indeterminate tomatoes, on the other hand, don't stop growing at a defined height. Instead, they continue to put on new foliage, flowers, and fruit for months until they're killed by frost.

Determinate tomato plants don’t need pruning other than removal of suckers (the little shoots that emerge where each branch meets the main stem) below the first flower cluster. Pruning above the first flower cluster results in loss of potential fruit because determinate tomato plants have a predetermined number of stems, leaves, and flowers hardwired into their genetic structure.

Indeterminate plants continue to grow and produce tomatoes throughout the season, you can produce only once a season, you would be reducing the overall yield.

Tomato plants typically begin flowering in June or July. Pruning tomato plants in the morning after dew or overnight rain has dried off the foliage, is best. It helps to prevent spreading plant diseases. Best to prune plants when the suckers are between 2 and 4 inches long.

To grow the strongest plant possible, prune side stems below the first fruit cluster. As a tomato plant matures, its lower leaves begin to yellow. Pinch or prune yellowed leaves to prevent disease, improve the plants appearance, and help the plant keep its energy focused on fruit production.

If your goal is to maximize the harvest, prune suckers sparingly.

Take care as many people who try pruning them back in the summer fail because the vines are pruned too severely this type of pruning opens the interior of the plant to intense sunlight, causing sunburn and the plants die. Remove about one -third of the plant and leave plenty of leaves to reduce sunburn.