Pruning Tomato Plants for Maximum Yield and Plant Health

Whether or not to prune tomatoes is perhaps the most famous debate amongst gardeners. There are a number of conflicting opinions about the benefits and drawbacks of pruning tomato plants, mostly regarding the removal of suckers.

Although letting suckers grow out can create new branches and thus more fruit, they should be kept under control to prevent tomato vines becoming a jungle-y and disease-prone mess.

So how do we reach this pruning balance and ensure our tomatoes are both high yielding and healthy? Let’s break it down section by section to really understand the ins and outs of trimming tomatoes.

Why pruning can be beneficial for tomatoes?

Why Pruning Can Be Beneficial For Tomatoes?

Pruning tomatoes is a subject of debate because it is thought that leaving branches and suckers to produce new fruit will increase yield. Although this is true and pruned plants may produce slightly fewer fruits, the fruits are more likely to succeed, reach a large size, and be healthy.

But make sure you check which variety of tomato you have, as even though determinate tomatoes can benefit from end of season pruning to ripen fruits, it is only the indeterminate varieties that need to be regularly pruned to control growth. 

A reminder: Determinate tomatoes (bush tomatoes) have a predetermined size they will grow to and will just provide one or two main harvests, and indeterminate (vine tomatoes) varieties will continuously grow and produce fruit until they are stopped by frost or another intervention. 

Here are the main reasons why pruning vine tomatoes can be beneficial: 

  • Pruning can improve airflow by thinning out the foliage between and within plants. As a result this reduces the likelihood of many disease pathogens breeding and spreading amongst your tomato plants. This is especially beneficial if you live in an area with lots of rain because the leaves will dry more quickly, and wet tomato leaves are very prone to fungal infections!
  • More space between leaves also allows you to spot and treat pest or disease presence more quickly. If your tomatoes become a tangled mess, it is very unlikely you will be able to see the underside of a leaf where eggs are being laid, or the early signs of a fungal infection before it’s too late.
  • Well pruned plants will provide you with more opportunity to see issues as they arise, especially as you will be working on the plants more often. 
  • Bigger fruits can be a notable benefit of pruning, as the plant is able to focus much of its energy on existing fruits instead of new growth. Although you may be able to get more fruits in theory without pruning, they are more likely to become damaged by disease or pests and may be smaller in size. 
  • You can fit more plants in your growing space when your tomatoes are kept in check, as you will have more space to plant them a little close to one another. This benefit can even make up for the slightly lower yields that result from pruning, while keeping the fruits large and healthy! 
  • At the end of the season for determinate tomatoes, and throughout the season for indeterminate tomatoes, pruning can help ripen fruits more quickly. Cutting back foliage around indeterminate varieties exposes them to sunlight which can allow sun-ripening to occur and enhance flavor (depending on the specific variety).
  • At the end of the season determinate and indeterminate varieties can be topped, which means cutting off their growing tip to halt all further growth. This directs all energy into ripening existing fruits before the frost.

When to prune your tomato plants?

When To Prune Your Tomato Plants?

Determinate tomato varieties should only be pruned right at the end of the season, when they are being topped to ripen the fruits.

Since determinate tomatoes have a predetermined growth pattern and will max out at a certain size, pruning is not necessary throughout the season. 

However indeterminate tomatoes are known to become monstrously tall and out of hand if action is not taken to prune back ambitious new growth, and should be pruned throughout the season.

Since the methods and techniques differ as the plant matures, the main pruning stages throughout the life cycle of a tomato plant can be divided into three groups: 

Early Season Pruning (Only Indeterminate)

The first point at which tomatoes can benefit from pruning is early in the season, right at the transplanting stage and for several weeks afterwards.

Depending on how tall your transplants are, this stage of pruning should take place when the tomatoes are 10-18 inches tall. This is when the plant is focused on establishing itself, so pruning is designed to facilitate that process. 

Mid Season Maintenance (Only Indeterminate)

Mid Season Maintenance (Only Indeterminate)

Pruning tomatoes in the middle of the season is focused on plant maintenance and disease prevention, and should be done continuously.

There are no strict guidelines on how tall the plants are at this stage, as they will be constantly growing and producing fruit! 

Late Season Topping (Both Determinate and Indeterminate)

The last time your tomatoes will get a pruning is at the very end of the season, and this is the only time determinate tomatoes should be pruned.

This is when the plants have reached their maximum height (for determinate varieties), or you want to stop their growth (indeterminate varieties) and get all the remaining fruits to quickly ripen up before the weather turns, at least 3 weeks before the first frost. Depending on your growing zone, this is usually done in the late summer or early fall. 

How to prune tomatoes

Whether you are pruning leaves, branches, flowers or suckers, you should always use sharp and clean pruning shears or scissors.

Make sure your hands are also clean and that the plants are completely dry to prevent spreading disease between them.

Here are the methods for pruning your indeterminate tomatoes at different points in the season:

1: Early-Season Tomato Plant Pruning 

Early-Season Tomato Plant Pruning

Right after your tomatoes have been planted, pruning is focused on helping the plant direct its energy towards establishing itself in the soil and developing a strong root system.

Here’s how to do that: 

  • Before you plant your tomato transplant, remove any lower leaves before the first main branch. This is so that you can bury your plant deep down in the soil. Fun fact: All those little hairs you see on the stem of your tomato plant? Those all have the potential to become roots, so burying them deep in the soil increases the amount of roots that can establish! 
  • Remove any flowers present (this can be done before or after transplanting). Although removing tomato flowers may seem counterproductive, it is actually important to keep removing them for the first week or so after transplanting, so that your tomatoes can focus on foliage and root growth before it starts worrying about flower and fruit production. This really sets your plant up for success!

2: Mid-Season Pruning Of Tomato Plants

Mid Season

Now your tomatoes have gotten out of their initial growing stages, they are probably beginning to set fruit and get some significant height.

Mid season pruning is all about maintenance and keeping a watchful eye out for diseases or pests that could compromise the health of your plants.

You also will notice continuously ripening fruit, and do some modified late season pruning at this stage. These are the basic steps of pruning tomatoes in the middle of the season:

  • Once you see the first fruit cluster form, prune any stray leaves and suckers that are attached to the stem below that point. You want the nutrients to shoot up the main stem and to the fruit, and not be redirected to lower, unproductive growth.
  • Eventually, these leaves will begin to naturally yellow, and in warmer regions that are in USDA zone 9 or above, you can leave them on the plant until they turn yellow to keep the ground shaded and cool. 
  • Keep removing suckers! This is the main component of mid season tomato pruning of tomatoes, as suckers will pop up with surprising frequency. In cooler, more Northern growing zones, remove almost all the suckers that pop up as the tomato plant grows. You could leave maybe 1 or 2 to develop at a time, and pinch off the rest with your thumb and forefinger when they are still small. 
  • For hotter, Southern growing zones, suckers should still be managed but you can use a technique called ‘Missouri pruning’, where just the growing tip of the sucker is plucked off, leaving a couple leaves to grow out and provide extra shade for fruit that could get burnt by the hot sun. 
  • While you are pruning tomato suckers, check for any signs of diseased leaves or fruits. Check the undersides of leaves for eggs and prune away any leaves that are developing dark brown or yellow spotting and either burn them or throw them away. 
  • As you see fruit clusters lower down the plant ripen, you can cut back some of the foliage if the risk of sun scald is not too large. Many varieties benefit from having their fruits receive.

3: Pruning Tomato Plant  Later In The Season

Pruning Tomato Plant  Later In The Season

At the end of your tomato growing season, you will want to prune both your determinate and indeterminate plants to help the existing fruits ripen up!

The first frost might be coming soon, and you don’t want your plant wasting energy on growing new flowers or leaves, you just want 100% of the energy to be on the fruits.

Follow these steps at the end of the season:

  • Using sharp pruning shears or scissors, cut the growing tips off your plants in a process called ‘topping’. There might be multiple growing tips, so make sure you chop them all off, a few inches from the top. 
  • For both varieties, but particularly your bushy determinate plants, you can snip away some of the thick foliage to expose your fruits to more sunlight and heat, especially for fruits nestled close to the stem. Be liberal! You can really hack away at all the foliage until your plants are essentially just stems laden with big bunches of tomatoes! 
  • If you are seeing diseased fruit at this point, pick it off and dispose of them to prevent any further spread while the rest of your tomatoes ripen. This is particularly true for those tomatoes showing symptoms of Anthracnose, which will easily spread to other fruits when it rains now that there is no foliage barrier between tomato clusters.

Tomato Pruning Tips To Remember 

Key Things to Remember
  • Check the variety of tomato you are growing, determinate varieties do not need to be pruned all season long- only topped at the end of their life cycle. Indeterminate varieties are the ones that need additional early and mid season pruning. 
  • Some common determinate tomato varieties include: Rutgers, Roma, Marglobe, & Celebrity. Common indeterminate tomatoes: Beefsteak, Sungold, Brandywine, & Big Boy. 
  • Clean equipment and clean hands are essential. If you are a smoker be especially careful since tomatoes are very susceptible to Tobacco Mosaic Virus. 
  • When pruning, try to leave as small a wound as possible by pinching suckers early when they are still small. Once suckers grow into thick branches, it becomes much riskier to cut them and leave a large gash where disease pathogens can easily enter the plant. 
  • Leave a few suckers to develop at a time, there is no need to remove 100% of them. Try to keep a balance where some new growth is allowed so more fruits can be produced, without compromising the benefits that pruning provides like better airflow, increased space, and disease prevention. 
  • Be patient with yourself and experiment with different pruning techniques to see what works for you. Many seasoned gardeners still discover new ways to prune and see their tomatoes have their best year yet!

Updated on by Amber Noyes

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