Pruning Tomatoes for plant health and production

Pruning tomatoes sometimes called “sucker pruning” can help your plants be more healthy and even more productive.

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Should You Prune Tomato Plants?

Let me start this whole discussion out by saying YOU DON’T HAVE TO DO THIS!  That’s right!   There are many years I barely bother with pruning tomato plants and they still continue to produce and be healthy.  But they are also a bit of a mess!  Unpruned tomatoes can get a bit unruly.  One of our favorite varieties “Sun Sugar” is particularly messy.  But if you don’t mind that, and you have sturdy tomato cages or stakes, then you really don’t have to prune tomato plants.

There I’ve said it!  Pruning tomatoes is a bit of a controversial topic in the gardening world.  Those that really push for it argue that plant health is improved (I agree with this one) and that fruit production and yield is increased and you may also have larger fruit (I think the science is still out on this one).

Those that don’t prune argue that it is a lot of work and that it really doesn’t improve the amount or quality of your tomatoes and the plants will do fine without it.

So as we tackle this topic today keep that in mind.  Other than a little lower branch pruning you could get away without pruning tomatoes and be just fine. But you do have to expect a large bushy plant to deal with.

If you are going to be pruning tomatoes in your garden.  Please be sure to use a good pair of Garden Pruners or a sharp knife.

I’ve put together a good description of pruning tomatoes below, but if you would like to see pruning in action then watch this video that I filmed:

Pruning Tomatoes – Determinate vs Indeterminate tomatoes

There are 2 types of tomatoes out there and you need to know what variety of tomato type that you have.  Determinate tomatoes are bred to stay limited in size and production.  This type of tomato grows to a “determined” size (hence the name) and needs very little if any pruning.  In fact pruning, determinate tomatoes will often reduce production with fewer fruit.  The only pruning I recommend for Determinate tomatoes is discussed in Step 1 below.

Below is a list of some Determinate varieties

Indeterminate tomatoes are not limited in size.  The plants can become very tall and very bushy, in certain situations this can be a problem.  If left alone and in warmer climates, indeterminate tomato plants are actually perennials and will just continue to grow longer and larger.  Indeterminate tomatoes are the type of tomato you can prune more aggressively.

Here is a list of some popular Indeterminate Varieties

Step 1 – Cleaning up branches touching the ground

Step 1 should be done, early in the season, once the plants are established and are starting to form fruit blossoms.

The first step in pruning tomatoes is to clean up the lower branches, especially the ones that are touching the ground.  Having branches and lower leaves touching the ground greatly increases the chances that a tomato plant will pick up a soil-borne disease such as fungi or bacteria.  And most tomato problems are soil-borne!

Before you start pruning tomato plants please make sure you are using sharp and clean pruners. Cleaning pruners helps to prevent the spread of disease.

I recommend that you clean up all the lower branches on your tomato plants.  Remove any branches and lower leaves that are touching the ground.  Look for the first flower cluster and you can remove all of the branches right up to the branch just below that first fruit cluster (but remember to leave that last branch).

Cleaning up the lower branches on your plants also has the added advantage of improving air circulation around the base of your plants.  This airflow also helps improve plant health by removing moisture around the plant, which is another source of plant diseases.

Step 2 – Cleaning up damaged or diseased branches

This step of pruning tomatoes should be done all year long.  Regardless of whether you are going to prune the rest of your plants or not.

This step involves just keeping the plant clean!  At least once a week throughout the growing year you should go through your plants and remove any branches that show signs of disease.  This is a good practice to help the overall health of your plants.  If leaves or branches are showing problems, just get rid of them!

Also, any branches that have been damaged by wind or other causes should also be removed.  A clean pruning cut will heal quickly and help protect the plant, whereas a damaged branch leaves room for disease or pests to attack your plants.

Step 3. – Sucker pruning tomatoes

First, off we should define what a “tomato sucker” is.  Suckers are branches or shoots that grow in the joint between a leaf branch and the main stem or “trunk” of the tomato plant. 

If left alone these suckers will become their own “main trunk”.  Those sucker trunks will then grow leaf branches and fruiting clusters of their own.  This can make for a very bushy and overgrown tomato plant.  Depending on the tomatoe varieties they really can get quite out of control.

Here’s where the controversy comes in.  Some growers feel a neat single “trunked” tomato plant grows bigger healthier fruit.  Others think why deny the plant every opportunity to produce as much fruit as possible?

I have always been on the bushier plants are better side of things,  but I am softening on that opinion and I have been pruning my plants quite a bit more the last few years, although I do still leave many suckers to grow, I’m just a bit more strategic about it now.

You will have to decide for yourself whether to sucker prune or not.

The actual pruning is quite simple, especially if you catch the suckers when they are small.  At that small stage, they can be simply pinched off between your fingers. 

Even when they are larger, the suckers usually snap off cleanly with little effort.  I seldom use clippers unless the sucker is very large!

Go through your plant and remove any suckers that you feel are going to cause the plant to become overrun!  Or you can remove them all, the main trunk of the plant will continue to grow upwards producing more leaf branches and flower clusters for additional fruit.

When you are getting ready to prune a tomato plant check to see that the plant is dry, pruning while the leaves or plants are wet can spread disease.

Step 4 – Maintenance tomato pruning through the season

Continue pruning tomatoes throughout the season removing any new suckers and any dead and or damaged branches to keep your plants clean and healthy.

As the end of the growing season approaches (4 weeks before your first frost), I would recommend removing all suckers.  Suckers divert energy to foliage growth, and as the season is ending you want the plant focused on ripening the tomatoes it already has. 

Step 5 – Topping tomato plants towards the end of the season

Something else for you to consider as the season starts to come to a close is the practice of topping tomato plants.  Topping is the practice of finding the “end” of your tomato plant’s main trunk and then cutting that terminal end off!  By removing the growing end of a tomato vine you stop the growth of the vines in that direction.  That will then allow the plant to put all of its energy into growing and ripening the tomatoes that are currently on the plant.

I think it is a good idea to do this about 4 weeks before your first frost.  Over those 4 weeks if the plant isn’t topped it will continue to grow and will produce more fruit flowers.  These new baby tomatoes will have ZERO chance of growing and ripening before the frost kills the plant for good.  So if you “top” the tomato plant then your plant won’t waste energy growing more fruit that will never ripen anyways.

If frost is threatening and you still have tomatoes that haven’t ripened you can learn how to bring those green tomatoes inside and ripen them there.  Learn how to ripen green tomatoes from this article.

And learn how to protect your tomato plants from early frost here.

Tomato Suckers can be rooted for new plants

If you are fortunate enough to live somewhere that has very long growing seasons (think zones 9 and 10) then you can plant tomatoes twice in the season.  A simple way to do this is to “clone” your tomato plants using some of the suckers that you have removed. 

Cloning is simple.  All you need to do is remove a sucker and then plant it back into the soil or into a container of potting mix.  Roots will form along the portion of the stem that you put in the ground and establish a new plant.  Be sure to keep the suckers well watered for at least 2 weeks during this process.

I hope this article helps you understand the practice of pruning tomatoes.  Remember, sucker pruning is something that doesn’t have to be done.  You can just let your plants go and you will still get a harvest.  But pruning tomato plants does make for neater, and often healthier plants.

Answers to a few common Tomato Pruning questions:

When should tomatoes be pruned?

You can start sucker pruning tomato plants once the plants are well established.  At least 2 to 3 feet tall.  The best time of day to prune tomatoes is in the morning on a dry day.  This will allow for the wounds to heal quickly with less chance of disease.

Should Tomatoes be pruned?

Some pruning to manage the size and air circulation of a plant should always be done.  Whether you prune the suckers on a tomato plant depends on how you feel about growing large, slightly out of control plants.

Should you cut the bottom leaves off tomato plants?

Yes, even on determinant tomatoes the lower branches below the first flowering bunch don’t serve many purposes and can be an easy route for the disease to enter the plant.  Remove these branches once the plant is established and is starting to flower.

How do you keep tomato plants from growing too tall?

Topping your tomato plants will keep them from growing too tall. This practice will also limit the number of flower bunches on the plant.  If a plant is getting too unruly in its height simply find the main trunk of the plant and cut it off at the desired height.  Then be sure to control sucker growth as well.