Determinate and Indeterminate Plants

Long, long ago, plants faced a pressing problem: How could they send out as many seeds as possible and ensure the survival of their kind?

In my new book, Leaves, Roots & Fruit, I talk a lot about plant motives. Plants are highly motivated to reproduce and leave behind as many genetic copies of themselves as possible. They can't move around and disperse their seeds wherever they'd like. Instead, they form enticing fruits to attract animals that can then spread the seeds around for them, either carried in their hands and eventually dropped elsewhere or digested and, well... eventually dropped elsewhere.

Each piece of fruit represents the plant's hope for survival. But how could they ensure those fruits do their part?

Instead of coming up with one solution to their problem, plants came up with two.

Indeterminate plants decided it's best to form and ripen their fruit in batches. If one truss of fruit is left to fall off the vine and land beneath the parent plant, maybe then the next set of fruits will be carried off somewhere new. This is the plant's way of not putting all its eggs in one basket.

Determinate plants, in contrast, decided it's best to form and ripen all their fruit at once. They're counting on a hungry animal (or human) coming along and finding the prospect of all that ripe fruit ready to enjoy irresistible. Basically, all the eggs are now in one really enticing basket.

Over the years, humans have intervened to modify plants to improve their size and flavor and even change their growth from indeterminate to determinate. The result is tons of options to choose from no matter what you want to grow.

Let's look at the two different growing patterns in more detail.

Indeterminate Plants

Many of our favorite fruits grow on indeterminate vines. Fruiting plants that vine include tomatoes in the Solanaceae family, cucumbers and certain types of squash (like winter squash) in the Cucurbit family, and pole beans and peas in the Fabaceae family. 

The word indeterminate means what it sounds like: not yet determined. In other words, these vines can be long. Very long.

You can either give these vines a structure to climb up and grow tall on, or you have to be willing to give the plant almost your entire garden bed so that the vines can spread all over. Indeterminate tomato plants, for example, regularly grow 10 to 12 feet tall. Thanks to their size, indeterminate plants typically need more space than a container garden can give them.

The main stem of an indeterminate plant will just keep on growing until something like frost comes along and makes it stop. That's because the plant forms all its flowers in little clusters along the sides of its stem, leaving the tip of each stem free to keep reaching higher and higher. I've even seen gardeners with really long growing seasons train a tomato vine over the entirely of their 8-foot-tall arch, turn it around, and let it grow back down the other way.

While the vine is climbing or spreading, the plant is typically forming flowers and immature fruits at the same time, all while it's still ripening older fruits. Small amounts of fruit will be ready for harvest each week, and the plant will continue to give you small harvests over the next 30 to 90 days or so.

The Benefits of Growing Indeterminate Varieties

• You can enjoy small harvests weekly from each plant from the time it reaches maturity to the end of your growing season. I'm not into canning or anything, so the idea of harvesting pounds and pounds of beans or tomatoes at once isn't appealing. I like to be able to harvest a little bit at a time to use fresh in meals.
• Vines can easily be trained to grow up a strong support structure, such as a beautiful arch trellis. Vertical gardening has lots of advantages, including freeing up more room to grow plants around the base of the vining plant.
• I often find pole varieties have an enhanced flavor. This is definitely the case with pole beans versus bush beans.

Determinate Plants

Other fruiting plants will grow wide instead of long. These plants include eggplants, peppers, and determinate tomatoes from the Solanaceae family; zucchini and squash from the Cucurbit family, and bush beans and peas from the Fabaceae family.

Many determinate plants are referred to as "bush" or "patio" varieties. Even though they don't need something to climb on, they may need stakes, small trellises, or cages to keep them upright.

Determinate growth is much more limited. Instead of ending with a growing tip, each stem ends with a flower cluster. This is basically a form of self-pruning. The plant will spend all its energy forming and ripening fruits from those flowers, instead of growing any taller.

As you might guess, bush varieties have a much smaller and more compact growing habit overall. While a vining tomato plant can grow upwards of 12 feet tall, a determinate tomato variety might reach no more than 4 feet tall.

Instead of ripening fruit in clusters and providing a continuous harvest, determinate plants will ripen the majority of their fruit at the same time. You might get a couple more fruits after the main haul, but you shouldn't count on it. You'll notice that the plant will start to show signs that its time in the garden is coming to an end. It came here, after all, to do a job, and it's now done that job.

The Benefits of Growing Determinate Varieties

• Determinate varieties grow well in containers and smaller garden spaces because they don't need as much room to grow and spread out.
• Since these plants are basically self-pruning, you don't have to worry about pruning these plants to promote more fruit growth. That's one less gardening task to do.
• Fruits are ready to harvest all at the same time. This is ideal for people who want to can their harvest or make large batches of recipes that use up their harvest. Many commercial growers prefer determinate varieties since the crop can be harvested by machinery all at once. That makes canning and processing food much easier.
• The fruits of many determinate cultivars mature earlier than their indeterminate counterparts. This makes determinate varieties great options for gardeners with shorter growing seasons.

Determinate vs Indeterminate Tomatoes: Which Is Better?

I wouldn't say one is better than the other. You can decide which type—bush or vining—works best for you and your garden by answering these three questions.

Question 1: Do You Want All Your Fruit at Once or in Small Batches?

I like to always have something I can harvest from the garden. So I prefer a vining plant that will produce fruit in clusters and give me more of a slow but continuous harvest that's easy to enjoy fresh. I'm not one to spend a lot of time in my kitchen processing and canning. Maybe I'll start canning fruits and veggies when my kids are all out of the house, but that just doesn't work for me now.

If you're someone who's interested in canning or making your own tomato paste, tomato sauce, or salsa, then a bush variety might work best for you because you're going to get a lot of fruit in one harvest. Bush varieties like paste tomatoes have also been bred to contain fewer seeds and more "meat", which makes them ideal for making sauces.

Question 2: Does Your Garden Setup Support a Vining Plant?

Like I said, vining plants tend to need a lot of space to spread out. If you don't have a raised bed with a trellis, then you're most likely better off growing a bush type of tomato in a container.

I have several arch trellises that are perfect for growing vining tomatoes, cucumbers, and pole beans. I train several cherry and grape tomato vines, both indeterminate, up and over my arch trellises every warm season and harvest clusters of tomatoes frequently from the vines. To me, there are few sights more beautiful in the kitchen garden than a large trellis covered in lush vines.

Question 3: How Long Is Your Tomato Growing Season?

Tomatoes grow outdoors between your last frost date in the spring and your first frost date in the fall. If you have a really long time in between those dates, you can benefit from growing vines that will produce almost that entire stretch.

If, on the other hand, you live somewhere with a season that's only a couple months long, you're probably better off growing determinate tomatoes. That way you know you'll get as many fruits as your plant can produce before the arrival of frost. (Or you could look for a short-season indeterminate variety.)

What Are Semi-Determinate Plants?

Semi-determinate varieties can sometimes represent the best of both worlds. They'll be bushier and more compact than indeterminate varieties, but they'll continue to grow through the season.

Semi-determinate plants often mature early (like determinate types). After their initial fruit production, they can typically be encouraged to form more fruits as long as their first fruits have all been harvested. Then, however, they might die back before the end of the growing season.

You'll find semi-determinate varieties of tomatoes, beans, and peas. They're usually hybrids that have characteristics that make them difficult to place firmly in one camp or the other.

Which Tomato Varieties Are Indeterminate vs Determinate?

When you’re planting your tomatoes, it’s important to have a handle on their growth habit before you get them in the ground.

Keep in mind that many of the kinds I list below can be found in both determinate and indeterminate varieties, so it's a good idea to check the back of the seed packet or the plant tag of the type you're growing.

Indeterminate Varieties of Tomatoes

Many of the heirloom tomato varieties you'll find to grow from seed are indeterminate. I love cherry and grape varieties because I can harvest a ton of them, cut them up, and use them just like I would a big tomato, but I don't have to wait around for a big tomato to form.

• Cherry Tomatoes
• Chadwick Cherries
• Sungolds
• Black Cherries
• Sweet Million
• Grape Tomatoes
• Juliets
• Golden Sweet Tomatoes
• Beefsteak Tomatoes
• Brandywine Tomatoes
• Cherokee Purple Tomatoes
• Green Zebra Tomatoes

Determinate Varieties of Tomatoes

These varieties are ideal if you're looking to can your tomatoes or make lots of salsa, pico de gallo, or tomato sauce.

• Roma Tomatoes
• Paste Tomatoes/San Marzano Tomatoes
• Rutgers Tomatoes
• Early Wonder Tomatoes
• Burbank Slicing Tomatoes
• Northern Delight Tomatoes

As you'll see from the tips below, pruning is really important with indeterminate vines to maximize fruit production. Follow these tips for vining plants:

-Install Trellis or Support Before Planting Indeterminate Plants

The best way to grow most indeterminate plants is in a raised garden bed with some type of trellis for the plant to cling to. Vertical growing more than doubles your productive space. With this type of setup, you can give each vining plant as little as 12 to 18 inches in width. 

-Prune Indeterminate Plants Down to One Main Stem

Think of your fruiting plant as a mini tree. You don’t see many mature trees that last for decades with a lot of trunks. There’s usually a thick main trunk, and all the rest of the plant’s extensive growth stems from that one source. With that in mind, prune indeterminate plants down to one main stem if they're branching out from the base. Do this within the first couple of weeks after transplanting them to the garden. Select the largest stem to be the main provider (the leader stem). Continue to prune back any new stems that sprout from the base of the plant. 

-Prune Indeterminate Plants Below First Flower

When the first flower appears, prune any branches and suckers below it. Let the plant branch out above the first set of flowers and become a canopy. Every two weeks, prune the lower branches on the vine, removing about a third of the plant’s leaves.

-Help Vines Stay Attached to Trellis

Use a gentle material like jute twine to tie vines to the trellis or support structure every couple of weeks, after you've pruned. Repeat every week or every other week. Pruning and training these plants upwards helps with airflow, which is really important for keeping diseases at bay, especially in humid climates.

-Prune Suckers for Larger Fruit or Leave Suckers for More Fruit

Most gardeners will tell you to prune the suckers (the leaves sent out by the plant in between the main stem and a side stem that will become a new vine). I leave the suckers because I've found they produce the most fruit. Basically, prune the suckers if you want to grow bigger fruit, and leave the suckers if you want to get more fruit. I don't know about you, but I don't care if my cucumbers or tomatoes can win a size contest.

-Keep Plants Well Picked

Harvest fruits or pods as soon as they're ready to encourage your plant to continue producing for you. You don't want to leave a mature piece of fruit on the plant for too long since it'll take resources from the plant that could otherwise go to forming new fruit.

-Top Off Vines Near End of Season

Two to three weeks before the season changes, top off plants so existing fruit will finish. Cutting those leaves and branches above any fruits tells the plant to focus all its energy on ripening the existing fruits.

Determinate plants are typically considered lower maintenance since they really don't need to be pruned to direct the plant's energy. You'll only need to prune discolored or damaged leaves or any leaves that are in contact with the soil.

Even though these plants grow much more compact, they often still need some type of support to prevent stems from bending or plants from toppling over. I mean, think about all that fruit that they'll have to be holding all at once!

One of the easiest ways to support bush types is with garden stakes. Simply drive a stake into the soil near the plant and then tie the plant to the stake with some loose twine.

You could instead use a small obelisk trellis or a tomato cage (I do not recommend tomato cages for vining plants), or you could set up a Florida weave.

Vining or Bush? You Decide!

Gardening is always a choose-your-own-adventure story. There's not really a right or wrong way to do things—just the way that works best for you. And there's not really one type of plant that's superior—just the type that you really like growing (and eating)!

Experiment with growing both types. Maybe you'll discover you prefer growing vining tomatoes but bush beans.

Thanks for being here and helping make gardening ordinary again!