Caring for staked tomato plants largely depends on whether you have determinate or indeterminate tomatoes planted. Determinate tomatoes, sometimes called "bush" tomatoes, have been bred to grow to a certain size and produce flowers and fruit at a certain time. Early tomato varieties are usually determinate and will not produce fruit further into the season. Indeterminate tomatoes will keep growing and producing fruit until the first frost, as long as you prune and harvest them regularly. Seed or seedling variety information will tell you whether your tomatoes are determinate or indeterminate.
Prune suckers on both determinate and indeterminate tomato plant varieties as soon as they appear. Suckers are small offshoots of the larger vines that bear fruit. To prune, grasp the sucker between your thumb and forefinger. Bend it back and forth until the sucker snaps off. Do not use pruning shears, as they can cause large wounds that leave your tomatoes susceptible to disease.
Apply tomato fertilizer per the manufacturer's instructions. Tomatoes are heavy feeders, so it is very important to make sure they have all the nutrition they need.
Water your tomatoes regularly. Blossom-end rot, which is exactly what it sounds like, is caused by a combination of steady heat and inconsistent watering. When tomato flowers have been fertilized, the tomato grows behind the flower blossom, which clings to the end of the tomato until it shrivels and eventually drops off. Make sure to water your tomato plants daily, especially in very hot weather.
Harvest ripe tomatoes regularly. This is less important on determinate tomato cultivars, as they will produce tomatoes only at a certain period in their growth no matter what you do. With determinate varieties, however, vigilant harvesting is the key to season-long production.
Prune suckers on indeterminate tomatoes as they appear. While you will have to prune determinate tomato cultivars only at the beginning of the season, the same is not true of indeterminates. Continual pruning drives the plant's energies into the tomatoes it is growing on its true vines.