What is a Tomato Sucker? (Should You Prune Them?)


Are you trying to figure out what a tomato sucker is, and what you should do with it?  If so, then you’re not alone.

So, what is a tomato sucker?  A tomato sucker is a small shoot that grows from a tomato plant.  A sucker will later become its own branch, producing leaves and energy for the plant.  Given enough time, a sucker may also produce flowers and fruit.

Of course, too many suckers on a tomato plant will make it difficult to manage during the growing season.  Let’s take a closer look at tomato suckers, along with when and how you should prune them.

Let’s get started.

What is a Tomato Sucker?

According to the University of Maryland Extension, a tomato sucker is a small shoot that comes out of an axil on a tomato plant.  An axil is where a stem and branch meet on a plant.

The stem on a tomato plant is like the trunk of a tree.  The branches on a tomato plant are just like the branches on a tree: they have leaves on them, and some of the branches produce fruit.

The image below illustrates what a tomato sucker looks like:

tomato sucker
A tomato sucker grows out of an axil, or the space between a vine and a branch.

In time, a tomato sucker will grow into a full-sized branch with leaves.  A sucker may also produce a flower cluster.

With proper pollination, some of the flowers in this cluster will ripen into fruit.  If you are worried about pollination due to lack of bees in your garden, check out my article on how to hand pollinate tomatoes.

You can leave suckers to grow on your tomato plants if you like.  However, some gardeners prefer to prune at least some of the suckers.

Should You Prune Tomato Suckers?

Whether you should prune your tomato suckers will depend on a few things:

  • Tomato type – determinate or indeterminate
  • Support method – cage, stake, or trellis
  • Sunlight – light intensity and exposure of fruit
  • Disease – early blight and other soil-borne diseases

Let’s explore each of these factors in a little more detail.

Tomato Type

There are two basic types of tomatoes: determinate and indeterminate.  You can tell the type by looking at the description in the seed catalog or on the seed packet.

The main difference between these two types is in how tall they get and how long they produce fruit.

Determinate Tomato Varieties

Determinate tomato varieties grow to a specific height (4 to 5 feet) and then stop growing.  They have a bush-like growth habit.

tomato plant with fruit
Determinate tomato varieties have a maximum height, and they only produce a set amount of fruit.

Determinate tomato varieties only produce fruit for a short time during the growing season.  After that, they stop growing and producing.

Since the amount of fruit is limited on a determinate tomato plant, it is not a good idea to prune the suckers.  Otherwise, you could be missing out on some of the already limited fruit that these plants produce.

Indeterminate Tomato Varieties

Indeterminate tomato varieties grow much taller, to a height of 6 feet or more.  They have a vine-like growth habit, getting tall rather than wide.

They continue growing and producing fruit throughout the growing season until frost stops them.

tomato plant
Indeterminate tomato varieties continue growing and producing fruit until frost.

Indeterminate tomato plants can get out of hand with too many suckers, especially later in the season.  For this reason, it is reasonable to prune some of the suckers to make it easier to manage the plants.

You can learn more about indeterminate tomato varieties in my article here.

Support Method

There are three basic ways to support your tomato plants: cages, stakes, and trellises.  The method you choose will depend on personal preference, but also on the types of tomatoes you grow.

Cages

A tomato cage surrounds a tomato plant and keeps it from falling over as it grows.  A tomato cage can be round or square, and is often made of metal, plastic, or wood.

plant cage
A tomato cage supports plants as they grow. It is ideal for determinate varieties.

A tomato cage is best for supporting shorter determinate tomato varieties.  However, you can use a taller cage for indeterminate varieties if you wish.

When growing tomatoes in a cage, there is less need to prune them.

You can learn more about tomato cages (and why to use them) in my article here.

Stakes

Stakes are often used to support taller indeterminate tomato plants.  However, you can use stakes to support determinate varieties as well.

tomato stakes
You can use long wooden, metal, or plastic stakes to support indeterminate tomato plants.

Stakes can be made of wood, metal, or plastic (for example, PVC pipes).  They should be tall enough to support your plants as they grow (this could mean stakes that are 7 feet or taller!)

It is often necessary to prune tomato plants that grow on stakes.  One reason is that it is easier to tie tomatoes to a stake when most of the suckers are removed.

Too many suckers will make it harder to tie the vines to the stake.  They will also make it harder to harvest the fruit later in the season.

You can learn more about supporting tomato plants with stakes in my article here.

Trellises

A trellis is another method to support tomato plants.  You can use a trellis as support for either determinate or indeterminate varieties.

wood trellis
A trellis is another option to support tomato plants as they climb.

A trellis can be made of metal, wood, or plastic.  Read my article here for more information on the various materials you can use for a trellis, and where to find them.

You might not need to prune tomato plants growing on a trellis.  The reason is that the suckers can grow right up the trellis and find their own way, without crowding other suckers.

Sunlight

You may not want to prune your tomato plants if they are exposed to full, strong sunlight all day.  The reason is something called sunscald.

Sunscald happens when the fruit on a tomato plant gets too much strong direct sunlight.  Normally, a tomato plant’s leaves absorb or block sunlight, preventing most of it from getting to the fruit.

sunlight through trees
Too much sunlight will cause sunscald on tomatoes.

However, if you remove too many suckers (and thus leaves) from a tomato plant, there may not be enough leaf cover to fully protect the fruit from sunlight.

At first, sunscald looks like tan, gray, or white blisters on tomatoes. Sunscald usually appears on the sides of the fruit, on the side of the plant that gets the most sunlight (or has the fewest leaves).

Eventually, black mold will find its way into sunscald spots.  For more information, check out this article on sunscald from Wikipedia.

Disease

If you live in an area with warm and humid weather, then you may want to prune at least the bottom suckers on your tomato plants.  This can help to prevent disease.

Many plant diseases can survive for a long time in your garden soil.  When it rains (or when you water plants), some of the water and soil can splash up onto the leaves of your plants.

If this soil is carrying disease, then your plant can become infected.  The disease can then spread from one plant to another, causing a big problem in your garden.

soil
Soil may contain plant diseases that can splash up onto the leaves of low-hanging tomato branches when it rains.

Pruning the lower suckers on your tomato plant will help to prevent this problem.  After pruning, the suckers that remain will not be touching the soil.

Also, water will not be able to splash up high enough to get onto the upper branches and leaves.

Pros and Cons of Pruning Tomato Plants

Below, I have included a table that summarizes the pros and cons of pruning tomato suckers.  More detail on the pros and cons follows the table.

ProCon
larger fruitless fruit
easier to
manage
plants
more work
to prune
less disease
from soil
more disease
from cuts
on plants
more plants
if you root
suckers
sunscald on
plants with
fewer leaves

Pros of Pruning Tomato Plants

There are several advantages to pruning the suckers on tomato plants:

  • Larger fruit – with fewer suckers, there will be fewer flowers, and thus fewer tomato fruits on the vine.  The plant can then focus its energy on growing fewer but larger tomatoes.
  • More manageable – with fewer suckers, it is easier to tie tomato plants to a support.  It is also easier to harvest the fruit when it appears.
  • Less disease from soil according to the University of New Hampshire Extension, keeping plants off the ground reduces fungal diseases, such as early blight.  Pruning off the lower suckers keeps the plant from touching the soil, where diseases may lurk.
  • More plants – if you wish, you can try to root any tomato suckers that you cut off of a plant.  If you are successful, you will get even more tomato plants, although they will have a much later start than your original plant.

Cons of Pruning Tomato Plants

For all of the advantages, there are also some drawbacks to pruning the suckers on tomato plants:

  • Less fruit – if you prefer lots of fruit, pruning is not for you.  You will get fewer flowers and fruit from both indeterminate and determinate tomato varieties if you prune them.  You can learn about how to get more fruit from tomato plants in my article here.
  • More work – it will take more work up front to prune the suckers from your tomato plants.
  • Infection – when you cut or break off part of a plant, there is a risk of infection by bacteria or viruses through the opening.  You need to weigh this risk against the reduced risk of disease from the soil getting onto low-hanging branches.
  • Sunscald – if you prune off too many suckers, the tomato plant will have fewer branches and leaves as it grows.  This reduced canopy will offer less protection against sunlight.  If there is not enough protection for fruit, they may get sunscald spots, which also invites mold and other problems.

How to Prune Tomato Suckers

After weighing the pros and cons, you may decide to prune off the tomato suckers from your plants.  If so, there are a few ways you can do it.

One way to do it is to snap off the suckers with your hands.  This is easier to do when they are still small.

Another way is to use a clean knife to slice off the suckers.  Make sure to wipe the knife with alcohol between plants to avoid the spread of any disease that may be present.

pruning shears
You can use a knife or pruning shears to make a nice clean cut when pruning tomato suckers.

Finally, you could use pruning shears to snip off suckers or even larger branches close to the ground.  Again, just make sure to clean the shears with alcohol between plants to avoid the spread of disease.

The University of Illinois Extension suggests pruning all suckers below the first flower (fruit) cluster on the plant.  One advantage of this method is that it will not cause sunscald, since all of the pruned suckers were below the lowest fruit.

Conclusion

Now you know what a tomato sucker is.  You also know how to decide if you should prune them, and how to do it right.

I hope you found this article helpful.  If so, please share it with someone who can use the information.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon

jonathon.david.madore

Hi, I'm Jonathon. I’m the gardening guy (not guru!) who is encouraging everyone to spend more time in the garden. I try to help solve common gardening problems so that you can get the best harvest every year!

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