Knowing how to choose determinate or indeterminate plants is an important part of growing tomatoes. You’ll see these words on seed packets, or on the tabs for tomato seedlings in your local nursery. But what do they mean? And why would you choose one over the other? This is a subject that befuddles many new gardeners, especially when growing tomatoes for the first time.
I’m going to explain it once and for all in a way that you can understand it forever. Forever!
Let’s start with the word itself: de-ter-mi-nate – From terminate, which means having a definite end. In-de-ter-mi-nate, then, would mean the opposite.
Growing tomatoes on a bush
Determinate tomatoes usually grow in a bushy shape, not too tall, and need little or no support. They reach a certain height, then pretty much stop. A classic example of a determinate tomato is the Roma.
Now there’s another thing that happens when a tomato has a definite ending. All of the fruits come ready around the same time, usually within a few weeks of each other. Then the plant stops making more flowers (and fruits), and dies. It’s terminal.
When you’re growing Roma tomatoes, chances are you’ll pick them and can them. They get so many in such a short amount of time. And Romas do make for a great marinara!
Growing tomatoes on a vine
Indeterminate tomatoes, on the other hand, don’t necessarily end, at least not as quickly as their determinate cousins. And they grow on vines, which just keep going and going and going…
When you see gardeners with tomatoes in cages that go 8 feet high, these are usually indeterminate, or vine tomatoes. If it were up to them, vine tomatoes would just snake happily along the ground, sharing their fruit with anything that wants to eat them (and in doing so, spread the seeds).
But just to be contrary, we humans like to lift them up out of the reach of snails, and rats, and whatever else might want to get into the garden. So we trellis or cage the tomatoes and encourage them to grow up instead of out. Not only does this keep the fruits safe from hungry pests, it also makes harvesting easier.
While their production does slow down toward the end of the season, indeterminate tomatoes will produce over a period of months, with fruits in all stages of growth.
On one end of the size spectrum, cherry tomatoes tend to be indeterminate, and on the other end you’ll find beefsteaks, with a whole spectrum of size, color and shape in-between!
If you’re in a mild enough grow zone, you can keep your indeterminate tomatoes growing for two, or sometimes even three years. And chances are, if the plant is at all prolific, and if you miss picking a few before they ripen and fall, by the time that indeterminate tomato vine is ready to give up the ghost, it will have a little baby vine popping up to replace it!