Tomatoes are successful home garden plants, and grow anywhere that offers warm summertime temperatures. These are not carefree plants, though, as they require good nutrition, consistent watering and feeding, and a trellis for support. Many gardeners choose to prune their tomatoes to allow the plants to put energy to fruit production rather than new growth. If you're going to prune your tomatoes, you must start with knowing what type of tomatoes you have.
Prune tomatoes based on growing type. Tomatoes grow in indeterminate types, which continue to grow longer vines as long as they're healthy, and determinate types, whose stems terminate in fruit clusters and grow only to specific lengths. Indeterminate plants are larger at 5 to 8 feet, while determinate plants grow only to 1 to 5 feet. Tomato seeds and seedlings are labeled as either determinate or indeterminate.
Prune indeterminate tomatoes throughout their lifetimes. Start by leaving two to three bearing vines off the main shoot. Find the first flower cluster on the stem and leave two suckers underneath. Prune off any suckers above the flower cluster and any suckers below your chosen shoots. Break off new suckers throughout the life of the plant, before they become 3 inches long. Bearing stems will produce more fruit without the additional suckers.
Prune determinate tomatoes once at the start of their growth, when they're 4 to 12 inches tall. Leave the main stem and one shoot, and prune away all other suckers. Allow determinate types to grow unpruned after that, as these bushes stay naturally bushy and controlled. Direct any new growth upward and tie it to the tomato's trellis. Additional pruning will reduce the bush's size and bearing ability.