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How To Prune Tomato Plants

If you’re confused about why or how to prune tomato plants, this guide has everything you need to know. Pruning tomatoes can make a big difference in the overall health of your plants and create ideal conditions for a better harvest. It’s one of the most important garden chores to make sure you get the best possible harvest of healthy, delicious tomatoes!

If you want to prune your tomatoes but you’re not sure how to go about it, don’t worry! By the end of this article, you’ll be an expert on how to prune tomato plants.

Person pinching sucker from a tomato plant.  Pinching is one method for how to prune tomatoes.

Types of Tomatoes That Need Pruning

When it comes to pruning tomatoes the first thing to think about is what type of tomato plant you have, indeterminate or determinate. Both need some pruning, but indeterminate varieties need much more pruning than determinate varieties.

Indeterminate Tomatoes

Indeterminate tomato plants continue growing and producing new branches, leaves, and flowers throughout the growing season. They can grow very tall and bushy and continue putting out fruit until the first frost. They can easily go wild and take over the garden if you don’t prune them. They need regular pruning to ensure both a good harvest and a healthy plant.

Indeterminate tomatoes growing on supports in a greenhouse.

Determinate Tomatoes

Determinate tomatoes have a predetermined size that they grow to based on their genetic makeup. They grow and produce leaves, then set fruit all at once. After fruit ripens, a determinate tomato plant won’t set any more fruit. Determinate varieties tend to be more compact than indeterminate varieties and stop growing once they reach a certain height so there is less concern of the plants getting too large and taking over the garden.

A tomato plant in a tomato cage.

Determinate tomatoes don’t need much pruning. Keeping the lower leaves away from the dirt and removing most of the suckers below the first flower cluster is all you really need to do.

Most of the information below applies to indeterminate varieties, but there are few things to keep in mind for determinate varieties as well.

Why Prune Tomato Plants

The main reason why you want to prune indeterminate tomato plants is to control where the plant is directing it’s energy. Pruning allows the tomato plant to put more energy into producing fruit and less into producing leaves.

Big bushy tomato plants may look like they’re healthy and thriving, but if all of that energy is going into producing and maintaining branches and leaves, you won’t get very many tomatoes. There are lots of other reasons to prune tomato plants as well, which we’ll explain below.

Pruning determinate varieties is very simple. You want to keep the plant healthy by removing damaged stems and make sure there is enough air circulation, but you don’t need to control it’s growth.

Determinate varieties put energy into growing branches and leaves first, then into producing fruit while indeterminate varieties try to do everything all at once.

Pruning determinate varieties too much will not help you get more or bigger fruit, it can actually reduce the number of fruit your plant is able to produce if you cut away too many stems where fruit would have developed.

Cherry tomato plants.

Control The Shape of Indeterminate Varieties

Pruning keeps tomato plants a manageable size and prevents them from sprawling all over the garden. You can direct tomato plants to grow on a trellis or other support so they’re easier to care for and harvest.

Improved Airflow and Less Disease

If the plant is very bushy and full of leaves it may not get adequate airflow, this applies to both indeterminate and determinate varieties but it is more likely to happen with indeterminate. Inadequate air circulation can cause the leaves to stay damp too long after a rain which makes the plant susceptible to mildew and other diseases.

Improved Access to Sunlight

Too many leaves can block sunlight from getting through and reaching all areas of the plant. This can make it harder for the plant to get all the energy it needs from the sun.

Tomatoes like full sun so if some of the leaves aren’t getting enough sunlight because they’re too crowded, those leaves may use up more energy than they’re producing and the plant won’t have as much energy to put into growing fruit.

Bigger fruit

Tomatoes require a lot of energy and nutrients to grow big, healthy fruit. If the plant is using all it’s energy to grow and maintain leaves and stems, you won’t get very many fruit, and the ones you do get will be small.

Pruning allows the plant to put more energy into producing fruit making it bigger and tastier-which is exactly what we want!

Closeup of three large red tomatoes on the vine.

Earlier ripening

Less energy going into leaves and stems means more energy going into the tomatoes which causes them to ripen earlier than tomatoes on unpruned plants.

You can ripen tomatoes even faster by pruning your plants to have fewer tomatoes growing at a time. When the plant is directing more energy to less fruit, they ripen faster. This can be helpful if you live in a climate with a short growing season.

How to Prune Tomato Plants

There are a few different methods for pruning and the steps you choose to follow may vary depending on your personal preference and the goals you have in mind. Let’s start with the basics that apply to most tomatoes.

Don’t Let Leaves Touch The Soil

Many of the diseases that commonly affect tomato plants come from the soil. Spores of diseases like tomato blight live in the soil and can easily be transmitted to the plants when it rains, especially when there are a lot of leaves near the surface of the soil. Rainfall and watering can cause the spores to splash up onto the lower leaves and infect the plant.

A tomato leaf infected with a disease.

To keep this from happening, remove lower leaves so that the lowest hanging leaves are several inches above the surface of the soil. This applies to both determinate and indeterminate tomato varieties.

Locate and Remove Suckers

Suckers are little stems that grow from the intersection between the branches and main stem of the tomato plant. If left alone, they can grow into full size branches and eventually produce some fruit

Suckers compete for energy with the main stem. By removing them, the plant will direct more energy into the existing stems and fruit. It’s okay to let a few suckers grow, you can get more tomatoes in both determinate and indeterminate varieties this way, but in indeterminate varieties the tomatoes will be smaller.

Removing suckers also keeps your plant from getting too bushy throughout the middle helping to maintain adequate sunlight and air circulation throughout the plant.

Short suckers that are under 4 inches long can be pinched or snapped off quite easily with your fingers. Bend the stem back and forth until it breaks off. Suckers that are thicker than a pencil will need to be clipped with pruning shears to minimize damage to the plant.

Person removing a sucker from a tomato plant.

Remove Flowers or Small Tomatoes

This is not a necessary step but it’s an option if you’re looking for a way to get bigger tomatoes from your plant. Find a cluster and pluck off some of the flowers or small green tomatoes before they get too large.

This allows more energy to be sent into the other tomatoes in the cluster, resulting in larger tomatoes that ripen faster. You’ll end up with less tomatoes but they’ll be bigger and ripen sooner.

Prune Disease and Damage

Any time you see signs of disease or damage you need to trim those stems off right away. By removing diseased branches early, you can prevent the disease from spreading or causing too much damage to your plant.

Any time you trim plants with signs of disease, make sure to keep the clippings out of your compost pile to avoid spreading the disease to other areas of your garden.

A tomato leaf infected with early blight disease.

Use Clean Tools

Keep your tools clean to prevent the spread of disease. You can use dish soap and a scrub brush to clean your tools and keep them in good condition. Rinse with water and pat dry.

Any time you’re trimming away diseased branches, clean the pruning shears with alcohol or another disinfectant to kill all traces of the disease and keep it from spreading to your other plants.

Make sure to you use sharp pruning shears or heavy duty garden scissors to prune your tomato plants for clean cuts. Using tools that aren’t sharp enough can create larger wounds that stress the plant and are harder to heal.

What will happen if I don’t Prune?

If you don’t prune a tomato, the plant will decide for itself where to direct it’s energy. If you’re dealing with an indeterminate variety, most of the time this means big bushy plants with a lot of spindly stems and very few undersized tomatoes.

If you have a determinate variety, the plant already uses it’s energy in a certain way to produce fruit so pruning is less important.

In any variety, not pruning at all increases the risks of problems developing including disease and inadequate airflow so it makes sense to do at least some basic pruning.

When To Prune Your Tomato Plants

The best time of day for pruning tomatoes is in the morning or evening when the sun isn’t too strong. Plants are most stressed during the hottest part of the day so you want to avoid adding more stress by pruning at those times.

You’ll want to start pruning tomato plants 2-3 weeks after planting and continue throughout the growing season. Regular, careful pruning will give you the results you want!

Early pruning

Early in the season you’ll be removing suckers and guiding the plant into the shape you want it to grow in. Suckers grow into large stems that compete with the main stem. It’s fine to leave a few suckers near the base of your plant if you’re going for 2-4 main stems.

When the plant is young those little suckers can grow into big stems pretty quickly so keep an eye on it every few days and pinch off the suckers you don’t want as soon as you spot them.

Person pinching a small sucker from a tomato plant.

When the plant is 2-3 feet tall remove the bottom sets of leaves so the lowest remaining leaves are several inches away from the soil to reduce the chance of pathogens in the soil splashing up onto the plant and causing disease.

Mid-season pruning

In the middle of the season your tomato plant will be taking shape and filling out nicely. This is when you’ll trim the middle to ensure proper airflow if you notice the plant getting too bushy. Remove any yellow stems and leaves from the lower portion of your plant as it grows.

You’ll still keep an eye out for suckers during the mid-season as well. Remove any suckers that appear beneath the first fruit clusters so they won’t take energy away from the developing fruit. Remove other suckers that you don’t want as soon as they appear.

Remember, it’s fine to let a few suckers grow on indeterminate varieties if you want to get more tomatoes, they’ll just be smaller. On determinate varieties letting suckers grow typically results in more tomatoes and won’t impact the size of the other tomatoes.

Late pruning

Towards the end of the growing season you can “top off” your indeterminate tomato plants by trimming the tops of the vines so the plant puts more energy into ripening the fruit that is already there, rather than growing taller and trying to produce more fruit.

This will prevent more flowers from appearing, but it will help the tomatoes that are already on the plant to ripen before the first frost.

As temperatures start dropping and it gets closer to fall, your tomato plant will start to slow down. Trimming the tops can help make sure your last tomatoes of the season are as big and tasty as the earlier ones.

Person using pruning shears to cut a tomato plant -- possibly topping off a tomato.

Things to Watch Out For When Pruning

It is possible to prune tomato plants too much. You don’t want to go overboard and end up hurting the plant. Pruning too much all at once can stress the plant unnecessarily so try to prune only a little at a time.

Tomatoes are solar powered. They need enough leaves on the plant to soak up energy from the sun that it can convert into sugar during photosynthesis. If there aren’t enough leaves on the plant, it won’t get enough energy to grow and produce.

In addition, if you remove too many leaves the tomatoes themselves can be exposed to too much sunlight which can result in sunscald. A good number of leaves are needed to shade and protect the fruit as it ripens.

Final Thoughts on How To Prune Tomato Plants

Three healthy tomatoes ripening on the vine.

Now you’re ready to get out there and work on your tomato plants! Did any of the information surprise you? Put some of these tomato pruning methods into practice and you’re sure to have a great tomato harvest this year. You’ll love having so many tasty homegrown tomatoes from your very own garden this summer.

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Ann

Wednesday 29th of June 2022

This article was so easy to understand and the pictures are so helpful. I am a first time grower and have read many articles but this by far is the best! Thank you.