Summer is here, your tomatoes are likely in the ground already but I am sure as you were buying your tomato plants and/or seeds you kept seeing tomato plants described as indeterminate or determinate. Let's explore.
Indeterminate tomato plants are plants that will just keep growing and producing fruit until they can't anymore because they die of some disease, get knocked over, a frost kills them, or you cut them off at the top to stop them from getting any taller.
Indeterminate plants can be pruned at your discretion. If you cut off a branch or two the plant will be able to make up for it if your growing season is long enough and you won't loose any fruit production. Many people choose to grow their indeterminate tomato plants with a main single stem and do not allow them to branch out. This is done to increase air flow and prevent disease, and of course some people just let them just do their thing with minimal pruning.
Indeterminate plants have the potential to get anywhere from four feet tall to eight feet tall depending on your weather and length of your growing season. This means they need a lot of space in the ground for their massive root systems and overhead space. Indeterminate plants also need to be trellised as they grow, but a tomato cage will not cut it, they will outgrow it very quickly. Florida weave, or single staking are much better methods for these mighty plants.
Determinate tomato plants are plants that will grow to a specific size (determined) and only produce a certain amount of fruit. Determinate tomato plants and are generally a smaller bushier plant.
It is very important that you do not prune determinate tomato plants because you will not get that fruit back if you cut off its branches. I will, however, encourage you to prune if the plant has a leaf that looks diseased or something along those lines, because if the whole plant catches a disease you will likely get no fruit at all.
Determinate tomato plants are perfect for growing in container, on porches, or in smaller spaces. They will still need some sort of support because once the fruit starts growing they can get heavy and they will start to lean and you don't want your plant to snap.
So before you plant your tomatoes, be sure you know if they are indeterminate or determinate so you can get the most out of your plants.