How to Prune Tomatoes the Right Way

Growing tomatoes is one of the easiest things you can do as a gardener, yet it’s certainly not without its challenges.

pruning a tomato plant
pruning a tomato plant

From watering to fertilizing, weeding to harvesting, there are all kinds of chores associated with producing a bountiful crop of delicious and juicy fruits.

Something I struggle with the most, it seems, is pruning my tomatoes.

It’s absolutely essential that you do this, though, particularly if you are growing a vining or indeterminate kind of tomato, like Big Boy and most heirloom cultivars.

That being said, you really do have to strike a fragile balance here. Prune too much, particularly if you are growing a determinate variety of tomato, and your efforts could prove to be counterproductive and even detrimental.

Here are some tips on how to prune tomatoes the right way – and why it’s so crucial that you invest the time in doing so.

How to Prune Tomatoes for Earlier Harvests, Higher Yields & Healthier Plants

Understand the Basics

Not sure why you need to prune tomato plants in the first place? The reasoning behind this is actually quite simple.

Tomatoes use the power of the sun to produce sugars. In the first month or two of growth, almost all of the sugar that the plant produces is directed toward leaf development.

Tomato plants will grow rapidly during this stage, often doubling their size every two weeks or so.

The plants will eventually begin to make more sugar than the growing plant can use, which will encourage them to make new branches and flowers.

Once the plant is about 12 to 18 inches tall, the plant will begin to exhibit some major structural changes.

The fruits will begin to tip the plant, causing it to lie on the ground (particularly if it is a vining type of tomato that would prefer to grow in a narrower, more upright fashion).

Left unpruned, a tomato plant can rapidly turn into an unsightly, disease-ridden mess.

Also, pruning a tomato will help divert some of the sugars from stem production to fruit production. You’ll have a steadier, more continuous supply of fruits when you prune your tomato plants.

Pruning can also improve plant health. When you prune the leaves of a dry, supported plant, they will dry off faster with each subsequent watering.

There is a reduced likelihood of fungal and bacterial pathogens affecting your plants.

Pruned tomato plants will produce fruits that are bigger – and that ripen earlier. This is something that is very important to note when you are growing tomatoes in a climate with a short growing season!

To Prune or NOT to Prune Tomato Plants?

Pick the Right Time

You can’t choose just any old time to prune your tomatoes – you’ve got to make sure you choose the most opportune moment to trim back your blooming beauties.

Before you start hacking, consider the type of tomato plant you are growing. Indeterminate tomatoes grow a lot like vines and must be trained and pruned readily in order to grow correctly.

Determinate varieties, on the other hand, will grow in more of a bush fashion.

Some common types of indeterminate tomatoes include Big Boy and German Queen, along with most heirloom and cherry tomato varieties.

Determinate cultivars include Heatmaster, Heinz Classic, and Amelia, just to name a few.

If you aren’t sure what kind of tomato you are growing, just look at its growth pattern. If it’s bushy, it’s probably determinate – if it seems to be growing in a vine pattern, it’s likely indeterminate.

Watch for Yellowing

For me, this is the easiest way to tell when my tomato plants need to be pruned. It’s pretty telltale!

I simply wait and watch, looking for the leaves and stems below the first set of flowers to become yellow. Once you notice this change occurring, you are ready to start pruning.

You can usually get rid of any yellow leaves on the plant, regardless of your pruning strategy.

These leaves are those that have been using more sugar than they are producing, and as your plant matures, these leaves will yellow and wilt.

Leaving yellowing leaves on your plant won’t do you any favors. Instead, it can increase the likelihood of disease. Remove them instead.

Create Space At the Bottom

Even if you don’t have time to prune your entire tomato plant, you can still give it a boost by pruning at the bottom of the plant.

A lot of the problems that arise in tomato plants, from disease to rot, come from the soil (tomato blight is one example).

Clear out the lower foliage, and you’ll reduce the likelihood of disease. This will also improve air circulation, something that is essential for the health of your tomato plants.

Use Sterile Equipment – and Work Only When It’s Dry

Whenever you are pruning tomatoes, it’s essential that you use sterile, sharp equipment. Dull blades rip and tear the plants, which can cause stress and further damage.

Sterilizing your tools is essential, too, to help prevent any kind of contamination.

Prune in the early morning or late evening and don’t prune in the heat of the midday sun – this is when tomatoes are most vulnerable to damage. Work on your plants when their foliage is dry so you don’t spread disease.

Mind the Suckers and Flowers

You will also want to keep an eye out for suckers. Suckers are small ew branches that will sprout in the spot where the stem meets a branch (on an indeterminate plant, anyway).

These suckers aren’t anything you want to keep on your plant, as they’ll sap energy from the rest of the plant as they grow and can result in tinier tomatoes.

Getting rid of suckers will help your plant produce more fruit (and larger fruits, too!).

You might also want to keep an eye out for flowers. Prune your tomato plants early on, ideally as soon as you notice flowers. This will usually occur when your plants are roughly 12 to 18 inches tall.

Get Rid of Any Dead or Diseased Plant Parts

You should also get rid of any parts of the plant that are dead, dying, or diseased.

You don’t have to follow any specific strategy for this but you can instead just remove these parts as you notice them.

This can actually increase fruit production and reduce the likelihood of disease.

How to Prune Tomatoes the Right Way: A Few Simple Strategies

1. Prune At Planting

When growing indeterminate tomatoes, you may want to consider pruning a small amount of the plant at planting time. Just remove the lower leaves so you can bury them deep into the soil.

You can also remove any flowers, if there were some present at planting time, so all of the energy of the plant goes into leaf and root development.

2. Remove Suckers and Leaves Below First Flower Cluster

The easiest way to prune tomatoes is to remove all leaves and suckers below the first flower cluster.

This can be done regardless of the cultivar of tomato and will help the plant stay strong and vibrant.

Most of the nutrients will be sent to the tomato fruits rather than being wasted on the tips.

To do this, you will remove a tip by the base, grasping it between your forefinger and thumb.

Bend it until it snaps from the plant. This technique works best when your plant is young, as the wound will heal rapidly.

If you have other leaves and stems growing below the first flower cluster, you have a few options.

If you are growing in a warm, humid environment like a greenhouse, you should remove all the pieces beneath the initial flower cluster to give the plant more “breathing room”.

If you’re growing in a warm zone, such as zone 8 or 9, you may want to leave these stems and leaves on the plant until they yellow, as they will help shade the roots of the plant in such a hot climate.

The only reason you want to remove these in a more humid setting is that the extra vegetation, coupled with the humidity, increases the likelihood of disease.

Ideally, you will remove suckers throughout the entire summer, about once or twice a week. They grow quickly!

3. Keep Thicker Shoots on the Plant

If you notice any thick suckers on the plant (usually, ones you’ve allowed to grow too long or haven’t noticed quickly enough) you will want to allow these to remain. Removing them could injure the plant past healing.

A good rule of thumb to follow is to measure the shot with a pencil. If the shoot is thicker in diameter than a pencil, just pinch the tip of the sucker, a method known as the Missouri pruning method. You can leave a couple of leaves behind if you’d like.

Just keep in mind that suckers will develop from this stem and you may have to do some extra pruning.

4. Prune Heavily on Indeterminate Varieties

If you’re growing an indeterminate variety of tomato, you can prune quite aggressively. Leave just five or six fruit beating branches, preferably those that grow above the wrist flower cluster, sprouting from the main stem.

That way, the plant will produce large and juicy fruits. If you leave too many of these branches, you’ll have small, sparse fruits.

The best way to do this is to choose a few of the strongest trusses and then pinch out the rest.

Just make sure, when you do this, that the vining plant is tied to supports. You don’t want the vine to crawl along the ground, as it can lead to rot and damage your developing tomatoes.

Keep in mind that this pruning method doesn’t work as well on determinate varieties of tomatoes.

They already have a set number of stems that they will produce so pruning above the flower cluster won’t do you any good but will just remove branches that could potentially produce fruit for you.

5. Simple vs. Missouri Pruning

Earlier in the article, I mentioned a method of pruning known as “Missouri pruning.” you might be wondering what makes this method different from other kidneys of pruning.

It’s simple.

With Missouri pruning, you are only going to pinch the tip of the sucker. One or two leaves will still remain.

This will allow the plant to maintain more leaf area for photosynthesis and it can also protect fruits from sunscald.

However, the disadvantage to Missouri pruning is that more suckers will develop along the side stems, so you will have to come back to it later.

Simple pruning is when you simply pinch off a sucker that you don’t want to become a stem. You must do this when it is small and succulent.

Simple pruning is best for quick pruning jobs, while Missouri pruning is better for large suckers and plants that have grown out of hand.

6. Top Your Plant

As you reach the end of the growing season, there is one more aggressive pruning strategy you can use on your tomato plants – it’s called “topping” them.

Roughly one month before you expect the first frost to hit, remove the terminal shoot of the plant.

The tomatoes that are currently growing won’t have much time to reach maturity – as a result, all of the nutrients the plant uptakes from the soil will be sent to the fruit, allowing them to ripen more quickly and readily.

What If My Plants Are Already Massive?

If you’ve stumbled across this article and your tomato plants have already grown out of control, don’t panic.

You might not be able to grow and prune your tomatoes on a vertical stake this year, but any kind of tomato plant (both determinate and indeterminate) will benefit from removing the lower leaves.

This will help prevent soil-borne pathogens from splashing onto the foliage.

To do this, simply clip back any leaves that are on the soil. Prune up to a foot away from the ground.

As your plants keep growing, you can continue to remove lower leaves to prevent any disease from spreading.

If you are growing tomato plants in cages, remove a few leaves from the center of the plant. This will increase airflow.

Don’t choose those that are above or below fruit cluster, as the leaves can help shade ripening fruit.

And next year, when you plant, factor in some time for staking and pruning your tomato plants.

Remember, pruning works best on plants that are strong and vigorously growing, so starting your tomato plants off on the right foot is essential.

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