Is Pruning Tomato Plants Necessary?
Do tomato plants need to be pruned?
In my first years of gardening, it seemed everyone told me, “yes.” But as I gained more experience and began listening to other gardening experts, I learned that the answer to this question isn’t as clear as you’d think.
People get passionate about tomato pruning. But I started asking myself, “why?”
Is it because this is the way they’ve always done it? Because their mom or grandpa told them that’s the best way to care for tomatoes? Or are people pruning tomatoes (or not pruning) based on their own experience and tests?
It seemed everywhere I turned I received conflicting information, so I did what I encourage every gardener to do. I tested it in my own garden.The results were so clear to me that I’ll never look at pruning tomato plants the same way again.
In this episode of the Beginner’s Garden Podcast, I talk about pruning tomatoes — how to do it, the potential benefits and drawbacks, and finally the results of my own experiment of pruning vs. not pruning tomatoes in my garden. Click below to listen or continue reading.
What Does it Mean to Prune Tomatoes?
When your tomato plants are growing, they have one main stem (sometimes two) growing up and lateral stems growing to the side. In the junction between these you’ll find a shoot often called a “sucker.” A sucker begins very small. But if left alone it grows into its own main stem that produces lateral stems and more suckers.
Which Tomatoes Do Not Need Pruning?
When we talk about pruning, we are talking about indeterminate tomatoes. Indeterminate tomatoes keep growing all season unless they are killed by frost or disease. Determinate tomato plants — like Roma tomatoes — produce all of their fruit in a big burst and then stop.
(You can learn more about these two types in my post about tomato trellis options for both determinate and indeterminate varieties. To find out which tomato plant you have, check the plant tag or seed packet.)
Regardless of whether you decide to prune suckers off your tomato plants, you won’t need to prune Roma or other varieties of determinate tomatoes. If you do, you will limit your harvest. For the rest of this discussion, we’ll talk about pruning indeterminate tomatoes.
Potential Benefits of Pruning Tomatoes
Prevention of fungal disease. Most people agree that pruning your tomato plants can help prevent diseases, specifically fungal diseases like early blight or septoria leaf spot. These diseases are characterized by yellow leaves at the bottom of your tomato plant. You can learn more about that here. In general, good air flow inhibits the spread of fungal diseases, and pruning can help open up the plant and increase airflow.
Tidy tomato plants. Pruning also keeps the garden area tidy. If you don’t prune your indeterminate tomatoes, they can get out of control. This can lead to difficulty in caring for the tomatoes and harvesting them. In some cases, tomatoes left on their own show signs of less overall plant health.
More sunlight on leaves. Another possible benefit of pruning is to keep enough sun on the tomato leaves. The thought is, lower leaves are unable to get the sunlight required for photosynthesis.
Larger tomatoes. If you do prune tomatoes, the plant will produce fewer flowers because of fewer suckers. Fewer flowers means fewer tomatoes. On the other hand, if your plant produces fewer tomatoes, the fruit may grow larger. In fact, a Purdue study found that there was a 25% increase in fruit size when the suckers are pruned.
Conflicting Opinions on Benefits of Pruning Tomato Plants
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Does sunlight ripen tomatoes? If you research whether you should prune tomatoes, you’ll find many opinions stating that the fruit will ripen faster because they have more sun.
But tomato growing expert Craig Lehoullier, author of my favorite tomato growing book, Epic Tomatoes, says that this is not true. He contends that shade produced by unpruned vines will not affect the ripening of the fruit.
However, I’ve observed that the gardeners who talk about this benefit live in cooler, rainier climates with less sun. It stands to reason they have a bigger problem with the shade.
Personally, when I prune my tomatoes in my hot and sunny Southern climate, sunscald is a huge problem because my tomatoes aren’t getting enough shade. Ultimately, you may need to think about your climate when deciding whether to prune or not.
Does pruning tomato plants shift sugar production from leaves to fruit? Another debated benefit is that energy, specifically sugar, goes to the growing fruit, not the foliage, when you prune. Others will say that it’s the foliage that makes the sugar so if you have more foliage you’ll have more sugar for the extra fruit. This is one question you’ll find multiple answers to and is best tested in your own garden.
Drawbacks of Pruning Tomato Plants
Disease pathway. When you remove the sucker, it opens a wound, which can become a pathway for diseases or insects. I’ve never noticed this in my garden, but I can see how it could be a problem. Pinching the suckers when they are small would limit the size of this wound.
Limiting photosynthesis. If the leaves produce sugar for the plant and the fruit, then with pruning, the plant loses some ability to produce that sugar.
Sunscald. Leaves shade the fruit, which helps to prevent sunscald. This is especially helpful if you live in a hot climate.
Less yield. I mentioned the Purdue study earlier that found pruned tomato plants produced fruit 25% larger than unpruned. The flip side of that study is that there was a 38% more yield in pounds from the unpruned plants. The thought is, then, if you prune your tomatoes you should get bigger fruit but if you don’t prune you’ll get more but smaller tomatoes.
Time commitment. The biggest drawback to pruning tomatoes for me is the time commitment. Depending on how many tomato plants you grow, this could be a significant time commitment to prune once a week.
Topping Tomato Plants When They Grow Too Tall
Toward the end of the gardening season, whether you choose to prune the suckers from your tomato plants or not, you may ask, “How do you keep tomato plants from growing too tall?”
You can top off your plant, which means to cut the tip of the main stem at the top of the plant. Then, the plant will use its energy to produce and ripen fruit and keep the plant healthy. This also helps keep your garden tidy and prevents your plant from toppling over, especially if you don’t have a trellis method in place to handle this tall growth. (Here are other ways to stake your plants to prevent toppling over that I’ve used successfully).
Experts recommend topping off your plants about 30 days before your average first frost in the fall. This will help direct energy toward ripening your last tomatoes.
Pruning Vs. Not Pruning: My Experiment
I want to encourage you to do your own experiment! Grow a couple of tomatoes you prune and a couple you don’t and see what works best in your own garden. Your results may very well depend on your climate, what varieties you grow, and many other variables. You should see what is best in your garden.
For my experiment, I grew two rows of indeterminate tomatoes side-by-side and staked them using my PVC/Rebar trellis method. I grew Black Krim, Arkansas Traveler, and Amish Paste varieties, and I pruned one and did not prune the other. As the harvest season progressed, I kept track of my harvest from each row — I tracked yield, approximate size of the fruit, and disease resistance.
I found that my unpruned row produced 37% more yield by the pound than my pruned row. I did not see any difference in size of the tomatoes between my pruned and unpruned row, either.
In addition, one benefit of pruning is supposed to be to have healthier plants but I did not find that in my garden. Both the pruned and unpruned rows were ruined by Septoria Leaf Spot equally.
(Interestingly, in a tomato planting in the other side of the garden, where the plants were spaced further apart in heavy duty tomato cages, but still left unpruned, I harvested tomatoes several weeks longer before they also succumbed to the disease.)
Should YOU Prune Your Tomato Plants?
Although the results of my experiment have led me to stop or at least limit the pruning I do on my own tomato plants, I do not necessarily believe my method is right for everyone. I hope you’ll test it in your garden like I did. But if you aren’t in the mood to conduct a science experiment, here are some questions that will help you make an educated decision for your garden this year.
How much garden space do you have? If you have less space, you might consider pruning more.
What kind of tomato support or staking will you use? Strong cages allow less pruning, while single-stem staking methods require it.
What is your climate like? If you’re in a hot, humid climate, less pruning will give ripening fruit more resistance to sunscald.
As you can see, we all will have slightly different variables in our gardens.
If you’ve ever tested pruning vs. not pruning tomatoes, what have you found? Comment below!
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Nice article! Unfortunately I can not grow tomatoes. We are surrounded on all four sides by black walnut trees, a few are huge trees and not on our property. I have tried several options, in a raised bed and also pots but there is only one place , right up close to our mobile home, where it has worked but not very well so I finally gave up. We love tomatoes though!
That’s unfortunate! Could you try containers?
Its my first time to listen to your podcast, but I have really enjoyed it. I will make effort to look for other topics because I really love gardening as I like organic vegetables.
Good job indeed. Thanks.
Great article, very well done! This is something I’m going to have to look at, too…
Greetings from Melbourne Australia
I grow lots of tomatoes and have always staked and pruned them.
Having moved into a brand new house with no established garden last year, (right on planting time) I did not have time to plant my usual variety. So I quickly purchased and planted some cherry tomatoes in a makeshift raised garden bed.
I happened to have 2 plants left over which I planted into the ground.
I painstakingly staked and pruned the garden bed tomatoes but didn’t even bother with the other 2.
Just as they were flowering and setting fruit I had to leave them in the trusted (LOL) hands of my teenage son while I visited my other son and his family in Vancouver for three weeks.
When I got back the pruned ones had grown out of proportion with suckers everywhere.
I madly pruned them and tied them. I find this job very time consuming and exhausting. I actually feel bad every time I cut off a sucker.
Meanwhile the other two were profusely flowering and setting hundreds of tomatoes.
I can honestly say that I got more tomatoes from the 2 wild plants than I did from the 6 pruned ones.
The only down side was I had to get down on my hands and knees to collect them. Those two plants were growing like a creeper plant. Two plants covered an area of approximately 6 feet by 10 feet. It was difficult to get to the middle to collect the tomatoes.
My two year old grandson and I loved to go out and collect the tomatoes. We would stand by the staked tomatoes and he would collect and eat the lower ones and I would eat the higher ones. Those babies were addictive. We just could not stop at 1 or 10 or 50.
Needless to say I will not be pruning tomatoes again. I will leave them as they are and be happy with whatever fruit they give me. I am not messing with nature. I will however tie them only so that I don’t have to get on my hands and knees to collect them.
I will try this experiment with my usual tomatoes (I grow the Kosovo variety ) and see what the results are.
Cheers from down under.
I bet that was a fascinating experience, comparing the two methods and seeing how they differed. Sounds like you had a lot of tomatoes to figure out how to use! 🙂 Thank you for sharing!
I really enjoyed your podcast. This is my very first time growing a garden in a raised bed, or any garden for that matter. I am scared to death that my tomatoes are all going to die. Prune vs not, too much water vs not enough, since the leaves look the same if they have too much or not enough. I am trying to enjoy gardening, but I am stressing over it instead! So I have decided to have my mind set as whatever is going to happen is going to happen! I am going to care for the garden the way I think I should after all the reading I have done. Thanks again for the podcast, very informative!
I think you have the right mindset. Tomatoes aren’t the easiest vegetables to grow, so give yourself some grace as you get the hang of it. And Mother Nature always has the final say! 🙂 I’m glad you found the podcast episode helpful!
Have you tried B.T. for septoria? It seems to work as a preventative. I just cut and dispose of (burn or trash in black plastic bag) infected lower leaves.
I’ve never heard of that. Thanks for the idea!
Well let me say this about pruning my tomatoes.
As long as the soil is kept aireated, properly drained, acid levels in check, there are no overly zealous nieghbors uphill from you who use chemical poisons. You water your plants from below and add a few amendments every so often. And most importantly support the ongoing growth of the plant by steak, trellis, baskets, etc. And keep pests in check. Plus enough sun. Well, it doesn’t really matter if you prune the plants or not. Some people do it just to feel like they are ‘gardening’.
Unless the plants get sick, pruning to me is just a visual presentation like a flower arrangement!
Gracias, por su valioso conocimiento.
Thank you for sharing your thoughts!
Interesting! I would have NEVER thought that it’s a good idea to prune branches off my tomato plants until the longer I gardened, I began to see “prune suckers” pop up in almost every tomato growing blog, article, and video. Funny how I didn’t have any issues with my tomato plants when I didn’t prune a thing. I have been OBSESSING over pruning the suckers this year mostly b/c it’s been so boring at home during COVID that I go check the garden like twice a day so it gives me something to do!! Haha! Now I would love to do a side by side comparison but I guess I’ll have to wait until next season.
I have one tomato plant that I bought at a farmers market that already had a MASSIVE sucker growing in the middle that I didn’t see until way too late – it’s got blooms and tons of branches on it so I guess that plant is only partially pruned. The plant is HUGE at 5ft tall and some branches stretching out 4-5ft and I’ve been having to tie them onto the cage. So I don’t know if the pruning is helping or hurting but it sure is producing fruit! Thanks for giving us a comparison. The fact that you got 37% more tomatoes and they produced longer in the non pruned row is enough evidence for me!
Greetings from Nigeria. Your podcast is so interesting and helpful. Have been making a lot of research on how to have a bountiful tomato harvest and I think have gotten the right ideas I need. I’ll be sure to bring you feedbacks on my harvest. Thanks and more wisdom.
I’ve found an earthbox container works great for tomatoes anywhere you have sun. You may also need a lit of water for it since the plants grow like crazy. You can still use a cage but may need support for that too.
i recently pruned the bottommost stems of my healthy tomato plants as i heard this was good to keep the leaves away from the ground. about 2 days after this they fell in a heap with bad wilt and some dont look like they will recover. Any ideas? the tomatoes were about a foot high when i did this
I’m sorry, Andrew, I’m not sure, unless the tomato plants weren’t large enough to withstand that pruning. (I usually don’t start pruning like this until they get a bit larger.) Otherwise, I wonder if your tomatoes had a disease unrelated to the pruning.