Want to grow a bumper crop of delicious tomatoes? Find out whether you should prune your tomato vines and remove suckers and how to grow new tomato plants from cuttings.
This is part of a series on 5 Best Tips for Growing Tomatoes.
How to Prune Tomatoes
First, the sucker mth. From the time I bought my first tomato starter plant many years ago, I have been hearing the same advice:
Don’t forget to prune your suckers!
If you don’t, the plant won’t have enough energy to fruit.
As it turns out, this is not true.
Suckers, or side shoots, are a normal part of a tomato plant, and they do not help or hurt the size or quality of the tomatoes.
It’s not like there’s a finite amount of growing energy and the suckers are depleting it.
The truth is, you can successfully grow all sorts of tomatoes without ever pruning them.
But, in some cases it’s a good idea. I’ve explained it all (below).
What is a tomato sucker?
Tomato plants have stems and leaves. Suckers are stems that grow between a stem and leaf, often growing out at a 45-degree angle.
Once a tomato plant is about 1 or 2-feet tall, you can see the different parts. A main stem is often the thickest part, and any side shoots or suckers look like additions.
If left to grow, a tomato sucker will act like its own main stem, adding leaves, flowers, and new suckers. And so on.
Old-school advice used to tell us to remove all of them.
The new way of thinking is to leave them on determinate (bush) tomato plants and decide selectively with indeterminate (vine) tomatoes. I’ll show you the difference (below).
On a side note, I’m sure the name ‘suckers’ doesn’t help! Don’t you think that makes it sound like it will do harm to the plant? But no. They’re just as much a part of the plant as anything else.
What are determinate and indeterminate tomatoes?
Determinates are (mostly) bush tomatoes and have a set growth limit (genetically pre-determined width and height), usually producing one harvest in 30-60 days. These are good for container growing, and rarely, if ever, need pruning. One exception is removing any shoots or suckers below the lowest fruit-bearing stem, simply because it’s non-productive.
Examples: Tiny Tim, Roma, Sweet ‘n’ Neat Cherry
Semi-determinates are determinates that produce a second set of fruit. An example is Roughwood Golden Plum tomatoes.
Indeterminates grow as vines, producing fruit ongoing, with one central main stem that just keeps going until a killing frost stops it, or when it has exhausted its lifespan (could be several years in the right greenhouse conditions). You may also hear them referred to as ‘tender perennials’.
Examples: Sun gold, Pink Brandywine, Big Boy, Red Beefstake
In general, you leave suckers on determinate tomato plants.
Selective pruning of indeterminates is recommended. There is more on this (below).
Which Type of Tomato Plant Do I have?
If you don’t know whether your tomato plant is a determinate or indeterminate, here’s a visual clue.
Once flowers are forming, check where they are located.
- Determinates form their flowers on the ends of branches/stems.
- Indeterminates form their flowers along lateral shoots.
How Can I Figure Out Which Variety of Tomato It Is?
To figure out your variety of tomato, often the ripe fruit is your best clue.
By the time you have ripe fruit, you know whether it’s a bush (determinate) or vine (indeterminate) type, and you know the size, colour, shape, and taste of the fruit.
Tomato leaves also vary greatly with different sizes, shapes, textures, and colours.
So, even with 15,000 varieties out there, you can probably figure out what you’ve got, or narrow it down to just a few.
There are also plenty of help sites online where you can post images.
If you’re looking for a thorough book on everything to do with growing tomatoes, check out Epic Tomatoes here on Amazon.
There is also a database of types of tomatoes here at Cornell University.
Here’s more info on a chart I created many years ago:
Providing Good Support
Tomato cages or other support systems are vital for bigger tomato plants. As mentioned in 10 Best Tips Before You Plant Tomatoes, it’s super smart to put any supports in place when planting a tomato because it’s hard to add them later without damaging the plant.
Give the main stem a stake (like a spine), and provide surface support for the branches/stems as they get weighed down with fruit.
Again, you could just let the plants sprawl, but staking and supports, plus the right pruning (see below) can offer these benefits:
- Allow light to reach all the leaves (for good photosynthesis)
- Provide good air circulation
- Help prevent the spread of soil-borne illnesses (by removing lower foliage close to the soil)
- Avoid fruit overload by limiting the number of productive stems
- Easy access to fruit (without missing any)
Pruning Indeterminate Tomato Vines
Okay, it’s time to learn how to prune.
So, we’re leaving the suckers on determinate (bush) tomatoes, and deciding what might benefit from pruning on indeterminates (vines).
Have a look at this video.
The goal is to have healthy plants that produce as much fruit as possible without risking damage (from the weight of the tomatoes) or disease.
A general guideline is to have about 4-5 productive stems (ones with flowers/fruit) on your indeterminate tomato plants. Each flower cluster can provide a handful of tomatoes, so that can mean 20 tomatoes per plant or more. This varies greatly, of course, depending on the variety and its size, but no matter—that’s a lot from just one plant, yet not so many that you risk losing them in an unfortunate incident.
In addition to removing some stems, toward the end of the growing season, we also may ‘top off’—pinch off the top of a main stem—of a tomato plant that has reached the top of its cage or supports (6-8 feet), or when there’s no value in it getting taller before frosts set in. When this is done, the plant is ‘topped’.
When we say ‘pinch off’, you may literally use your fingers to remove the sucker right at its base. Alternately, you can use fine, clean scissors or a sharp blade. You’ll get a feel for it as you try it. The less damage or open wound on the main plant, the better, of course.
Organic Slow-Release Tomato Fertilizer
Rooting Suckers for New Plants
There’s two options when removing suckers. You can pinch them off early on and discard them, or, if you want to root them for new plants, let them grow to at least six-inches on the main plant, and then remove them.
Pruned suckers can be rooted in warm water or potting soil, providing an exact clone of the main plant.
Rooting suckers is a good way to provide back-up plants in case of storm damage. Or, you can give them away to garden friends if there is enough time left in the growing season.
Growing Tomatoes Indoors
The only reason most tomato plants from the outdoor growing season will perish in fall is because of cold temperatures, so why not keep them going?
I started a tradition several years ago where I take tomato cuttings from healthy plants in early fall and root them indoors.
You could also transition whole potted plants.
The first few years I always chose cuttings from cherry tomato bushes. I just keep them plant by a window, which is a bit too drafty and by no means optimal, but I still managed some years to end up with flowers and fruit—three small ripe gold tomatoes!
Most recently, I accidentally rooted a larger variety and much to my surprise, it produced one, big beautiful ripe red tomato.
So who knows what’s possible? Sometimes there’s just enough of the right conditions to make it work.
You can read more about growing tomatoes and other crops indoors here: How to Grow Vegetables Indoors Year-Round.
Pruning an indeterminate tomato plant isn’t a one-time event. As the plant continues to grow, new suckers will form. If you stick to the goal of having 4-5 main stems (that are flowering and fruiting), it’s easy to see which suckers should be removed and what to leave on the plant.
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- Leave suckers on determinate (bush-type) tomato plants.
- Indeterminate (vine) tomato plants do best with 4-5 main flowering/fruiting stems. Remove any additional suckers.
- If you wait until suckers are at least 6-inches long before removing them, you can grow them as new plants by rooting them in water or organic potting mix.
- With the right growing conditions, you can also grow tomato plants indoors as houseplants. Indeterminate cherry tomato varieties may produce small amounts of ripe fruit indoors. But don’t hold your breath.
~Melissa the Empress of Dirt ♛