Updated: July 9, 2020
What are the benefits of pruning tomato plants? That all depends on what you want. Ask yourself this question: Do you want five or six gigantic and spectacularly, flavorful tomatoes, or do you want 10 to 20 medium sized tomatoes with pretty good taste?
Maybe you want both. In other words, you want to grow some of your plants for maximum tomato size and others for greater numbers of fruit. With proper pruning, you are in control.
Let’s take a sec to get the legal words out of the way. This article may contain affiliate links. That means if you click and buy from my partners, I will make a tiny amount of money at no cost to you. This in no way affects my recommendations.
Of course, genetics plays a critical role, too. You are not going to get really large tomatoes from a grape tomato plant. Likewise, you are never going to millions of Pineapple tomatoes. Ridiculous!
The way I look at it, why grow something that is only a little better than what you can get in the grocery store. Go for the gold!— Suburban Hobby Farmer
The way I look at it, why grow something that is only a little better than what you can get in the grocery store. Go for the gold!
So this article covers my pruning tomato plants strategy for growing really big slicing tomatoes from indeterminate varieties.
Table of Contents
This is a long, detailed article. You can jump to where you want to be by clicking on the different sections below. To come back to this table of contents, just use the back button on your browser.
- Pruning tomato plants
- Plant parts defined
- Pruning while transplanting
- Pruning to the first fruit cluster
- Pruning suckers
- Single leader stems and line trellising
- Missouri pruning
- Hoop house growing: the benefits of pruning tomatoes
- Toping the plant and root pruning
- Pruning Tomato Plants FAQ
- Fewer but bigger tomatoes
Pruning tomato plants
Tomato plants are all about taking nutrients and water from the ground and sunlight from their solar panel leaves and combining them to make plant sugars.
You should think of these sugars as “energy” that the plant uses to do things. For example, the plant can use this energy to make more roots, leaves, flowers or grow fruit.
At first, a tomato plant will focus sugars mostly to grow its tip (the very top part). But once it starts producing more plant sugars than it needs for this, it can do other things.
Typically, it reaches this “sugar tipping point” when it has:
- Recovered from transplant shock (about 3 – 4 weeks after transplant)
- Has over a dozen leaves
- Receives eight to 10 hours of sunlight a day
At this point, it uses the extra sugars to start growing suckers and then flowers.
Plant parts defined
When it comes to tomato plant pruning, there are six plant parts you should be able to identify: leaves, flower cluster, main stem, side stems, suckers and tip.
Leaves. These are pretty easy to identify. Leaves use photosynthesis to make plant sugars. Leaves grow on leaf stems that grow off of the main stem or side stems. Do I need to say more?
Flower Clusters. These also are easy to identify. Tomato flowers, once pollinated, turn into tomatoes.
Side Stems. These start as suckers, but grow into branches with leaves and eventually tomato clusters of their own. They come off of the main stem. When you are looking at the top of the plant, it’s sometimes hard to tell a side stem from the main stem. A side stem is often taller than the main stem.
Main Stem. This is the stem that leads from the roots to the rest of the plant. It is the main highway for getting plant sugars to and from where the plant needs them. It’s important that the main stem is strong and vigorous. Leaves and flowers grow off of this.
Suckers. Suckers are subordinate stems that grow in the crook (technical term is the axil) of the leaf stem and main stem. Suckers, if unpruned, grow into subordinate stems with leaves and flowers of their own.
Tips. These are the center, top part of a main stem or side stem. Tips are where plants grow taller. They are the very top of the stem. Sometimes they aren’t the highest part of the plant because leaves sometimes grow taller than the tip.
Related: Better Tomatoes with Walls of Water.
Pruning while transplanting
The first time you should consider pruning is when you are transplanting your plants into the ground.
It’s good practice to remove the first two or so leaf stems so that you can bury some of the main stem in the ground. Burying the stem encourages root growth from the underground part of the stem and gives your plant a good start.
Removing the first two branches makes space between the ground and your next leaf stem. This added space keeps water from splashing up onto the leaves when it rains and gives you room to water without getting any leaves wet.
Sometimes I mistakenly bury the plant too deep so there is no room between lowest leaves and the ground. Don’t do this! You don’t want your flower clusters or leaves too close to the ground.
One of the main rules of tomato growing is to do everything possible to keep your leaves dry. You especially don’t want water bouncing off the dirt and onto the leaves. Water bounce is one of the main causes of tomato plant disease.
Pruning to the first fruit cluster
Once the flowers on the first cluster change into fruit, many people prune all the leaf stems (and leaves) below the first cluster.
If you don’t leave one leaf stem above and below the cluster, the tomatoes in that cluster will grow very slowly.— Suburban Hobby Farmer
Removing these leaf stems makes it easier to water and focuses the plants energy on growing up.
But I don’t prune to the first cluster.
Instead, I always leave one leaf branch below the cluster. Why? The leaves just above and just below the cluster supply the most plant sugar to the fruit.
If you don’t leave one leaf stem above and below the cluster, the tomatoes in that cluster will grow very slowly.
That said, even if you remove the leaf stems closest to the cluster, there’s probably enough sugar in the stem to feed the fruit so they ripen.
But I want the biggest and sweetest tomatoes possible. So I don’t take any chances. I don’t prune these leaf stems.
Related: Should you mulch raised garden beds?
What are tomato suckers? They are side stems that sprout in the crook between the main stem and the side stem.
Suckers get a bad rap because they sap strength away from the main stem. One important goal of tomato pruning is to have a strong vigorous main stem.
So a lot of people simply pinch them off when the suckers are small.
This focuses the plant’s energy on growing taller, making bigger fruit and improves sun penetration to the lower leaves. All good things.
Still, there are reasons not to do this.
First, each side stem will have many leaves and fruit clusters of their own. You may want more fruit (even if it means smaller slicing tomatoes).
Growing out suckers is the way to do this.
Growing out these side stems is essentially growing a whole new plant with leaves that supply sugar to the new clusters.
Second, every time you cut the plant, you increase the chances of disease. Obviously, you want to minimize the chances of a sick plant.
Single leader stems and line trellising
Indeterminate tomato plants are vines and, as a result, will NOT grow upright unless they are trellised.
There are three popular methods of trellising tomato plants to keep them off the ground:
- Staking and tying
- Line trellising
I use line trellising to support my tomato plants. If you are not familiar with line trellising, it involves suspending a vertical line from overhead to the ground and training the vine so that it grows up the line.
To make line trellising work, you need to prune to a single stem. This is because the line must wrap around the stem to hold the plant upright.
With trellising, if you have side stems they will have no support and probably break off when tomatoes grow heavy.
Pruning to a single stem means removing all suckers before they grow into side stems.
Line trellising comes in handy when you prune to a single leader. This is because you can to lower the plant by unwrapping the line.
As a result, you can continue growing and supporting your plant even after it reaches the top of the line. You just lower the plant by unwrapping the line so that the first cluster is about six inches off the ground.
You can do this for as long as you don’t have frost. The leafless stem curls around at the bottom of the plant.
This allows the plant to continue growing up from the tip and making new flowers and fruit. It also ensures that all the leaves get sunshine.
Single leader pruning and line trellising promotes healthy plants that successfully grow large fruit.
Of course, if you prune all suckers before they grow substantial leaves, your plants will have fewer sugar producing leaves.
One way to take advantage of sucker leaves without growing side stems is Missouri pruning.
This involves letting two leaf stems grow from a sucker, but pinching off the very tip of the sucker so that it doesn’t grow into a side stem.
This works well in several situations. You can use Missouri pruning when:
- You want to remove suckers but don’t have too many leaves on the plant to support fruit growth.
- The sun is very intense for long periods and you want leaves to shade the fruit so they don’t get sun scald.
- Your suckers have already grown into stems, and you don’t want to shock the plant by removing large portions of it.
Hoop house growing: the benefits of pruning tomatoes
If you are growing tomatoes in a hoop house, and I think you should, there are two special considerations.
First, backyard hoop houses are smaller than their commercial cousins. So space is limited.
Hoop house growers need space to get at weeds and to water. Another important consideration is top dressing with compost is a difficult task when there isn’t enough space between the plants.
Line trellising in this environment is definitely an advantage. This is because line trellising and single leader pruning trains plants to grow tall and thin. The result is fewer but more efficient plant leaves.
Second, maintaining air flow, even in a smaller backyard hoop house, is important. If plants are blocking air flow, temperatures and humidity in the summer will be high.
High temperatures reduce fruit growth. High humidity, when excessive, promotes disease.
In a hoop house, tall thin plants are an advantage.
Toping the plant and root pruning
There are two types of pruning that will help ripen fruit more quickly.
At the end of the growing season when it becomes obvious that your tomatoes won’t ripen before the first frost, you can (1) top your plant and (2) root prune.
Topping the plant is when you remove the tip of the stems. This signals to the plant that it should stop growing new leaves and fruit and put its energy into ripening the existing fruit.
Root pruning involves damaging the plant roots. You can do this by sticking a pitch fork in the ground about two feet from the stem and lifting up the center of the plant enough to sever the roots on one side.
You don’t have to upend the plant. All that’s needed is to trim the roots.
Like topping, root pruning signals to the plant that it has suffered mortal damage. As a result, the plant will put all its effort into ripening the fruit.
When used in tandem, topping and root pruning are sometimes enough to ripen fruit early enough to beat the first frost.
Of course, many people prefer to make green tomato relish or fried green tomatoes with their green fruit.
Pruning Tomato Plants FAQ
Here are some of the most common questions I get about pruning for the best possible backyard tomato harvest:
You should prune tomato plants if you are growing large slicing tomatoes on indeterminate plants. Pruning allows the plant to focus plant sugars on making fewer, but larger tomatoes. It also makes leaves more efficient because fewer leaves are shaded. You don’t need to prune when growing determinate tomato varieties or when you want more tomatoes.
Don’t prune tomato plants until they (1) have recover from transplant shock, (2) have at least a dozen leaves and (3) receive eight to 10 hours of sunlight each day.
If you want larger, more flavorful tomatoes, you should remove suckers before they become side stems. This is called pruning to a single leader. You also should remove all leaf stems except one before the lowest fruit cluster. This will help prevent disease and make it easier to water your plants without getting the leaves wet.
Many people suggest removing flower clusters before transplanting. This isn’t necessary for strong root growth. In fact, you will get ripe tomatoes sooner if you DON’T do this. I suggest you leave the flowers on and tap the flowers slightly with your fingers when the flowers are fully grown out. This will pollinate the flowers sooner and start tomatoes growing earlier. You can start pollinating these flowers either before or after you transplant. If you do this, you will get tomatoes sooner, as long as there is enough sun, the temperature is right and your plants don’t suffer too badly from transplant shock.
There are two kinds of tomato pruning that will help speed up the ripening process. The first is topping the plant. This is where you cut off the very top of the main stem and side stems. The second is root pruning. This where you cut the plant roots by by sicking a pitch fork in the ground about two feet away from the stem and pull up on the plant. These two pruning methods signal to the plant to stop growing leaves and flowers and ripen the fruit.
If you want to grow large, flavorful, slicing tomatoes, you should remove all the leaf stems below the first tomato cluster except the one just below it. The leaves above and below the cluster most directly supply plant sugars to the tomato. You also remove all the suckers before they become side stems. This will focus the plant on growing tall and helps make the remaining leaves more efficient.
When transplanting tomato plants you should bury some of the stem to promote strong root growth. To make this possible, you should remove two or maybe three leaf stems from the plant. By removing these leaves, you will add room between the ground and the first set of leaves. This space is very important because you want to do everything you can to prevent water from bouncing off the dirt and onto your tomato leaves. Water bounce frequently causes tomato plant disease.
Space in a backyard hoop house is often more limited than commercial hoop houses. So you should prune tomato plants to a single leader and line trellis them. This makes for the most efficient use of space and promotes air flow through the plants. Good air flow in a hoop house is important because it helps tomato plants dry more quickly and reduces chances of disease.
If you want to grow bigger slicing tomatoes, you should remove all suckers before they turn into side stems. As a result, you will have fewer tomatoes, but they will make up for it in larger size. Pruning suckers also will reduce the amount of leaves that are shaded. This means that the leaves will be in sun for more time. More sun will make the leaves more efficient at producing plant sugars. Plus, the leaves will dry off more quickly and be less susceptible to disease. All good things!
Tomato leaves turn yellow for a number of reasons. One common reason why leaves turn yellow at the bottom of the plant is because they are being shaded by the upper leaves. When a leaf requires more plant sugars than it produces, the leaf will turn yellow and eventually die. Pruning can help keep leaves healthy in the lower part of the plant.
Fewer but bigger tomatoes
Pruning to a single leader will most definitely reduce the number of tomatoes you harvest. This is true because there will be only one fruit bearing stem instead of many.
But the fruit will be bigger and will make up in weight what was lost in in numbers.
The plant also will stay healthier longer because pests will be easier to spot. Also, leaves will not be contaminated from water bouncing off the ground.
If you haven’t already, give it a try.
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