Understanding the differences in how determinate and indeterminate tomato plants grow and set fruit can help you choose the best type for your home garden. The differences can influence not only which type you choose, but also how the plants should be spaced, trellised, and pruned.
Differences between the growth types
Plant size at maturity
The first difference that we can easily see in the garden is how large the mature plants become.
Determinate tomato plants usually grow between one and five feet in height, which means they are less likely to overwhelm a small garden. Many patio and container type tomatoes have a determinate growth habit.
Indeterminate tomato plants can grow to become much taller, as much as 8 or more feet tall. Main stems of plants in this growth type continue to grow in length/height for as long as they are healthy. Many heirloom varieties are indeterminate type tomatoes.
Semi-determinate tomato plants are a third growth type that you may see. As you might have guessed, the characteristics of a semi-determinate plant are in between those of the two other types. These plants are a little less tall and rangy than indeterminate type tomatoes, but not as compact as determinate types. This growth type can work well in a small garden.
Differences in when they set fruit
Timing of fruit production and ripening — when it is ready to harvest — is another difference between the growth-types that we can see in the garden.
Determinate type tomato plants set almost all of their fruit within a few weeks, and then their productivity slows way down. The fruits form on side-branches that are fairly closely spaced on the plants.
Indeterminate type tomatoes produce fruit all summer and into the fall, if they stay healthy. The fruits are spaced farther apart on indeterminate plants than they are on determinate plants.
Semi-determinate type tomatoes can produce fruit through the whole season, but they may not be as productive toward fall as an indeterminate type.
source: smallgardennews.com