Your Cool Home is supported by its readers. Please assume all links are affiliate links. If you purchase something from one of our links, we make a small commission from Amazon. Thank you!
Pruning grafted tomatoes is all about balancing the plant’s energy between the vigorous rootstock and the productive scion.
When you prune grafted tomatoes, you’re not just trimming leaves, you’re actively directing the plant’s growth toward fruit production while keeping that strong graft union healthy.
If you’ve ever wondered how to prune grafted tomatoes without ruining the graft or stunting the plant, you’re in the right place.
Grafted tomato plants are different from your standard varieties because they have two parts: the rootstock (the bottom) and the scion (the top that fruits).
Pruning grafted tomatoes requires a slightly different approach than pruning regular tomatoes, and I’m going to walk you through it step by step.
In this post, we’ll cover why pruning grafted tomatoes matters, when to do it, and exactly which shoots to remove so you get the biggest, tastiest harvest possible.
Let’s dig in.
Why Pruning Grafted Tomatoes Is Different and Essential
Pruning grafted tomatoes is essential because the rootstock can send up its own shoots, and those will compete with your fruiting scion for nutrients.
The whole point of grafting is that the rootstock provides incredible disease resistance and vigorous root growth.
But that vigor can backfire if you let the rootstock take over.
When you prune grafted tomatoes correctly, you ensure all that root power goes straight to the fruit you actually want to eat.
1. The Rootstock Shoots Are Your Enemy
The single most important reason to prune grafted tomatoes is to remove any shoots that emerge from below the graft union.
These are rootstock shoots, and they will be more vigorous than your scion shoots.
If you leave them, they’ll suck energy away from your fruiting branches and may even produce inferior fruit or no fruit at all.
Check the base of your plant every few days and pinch off anything that appears below that distinct graft scar.
This is the number one mistake gardeners make when they prune grafted tomatoes.
2. Encouraging Strong Scion Growth
Pruning grafted tomatoes also helps your scion develop a strong central stem.
Because the rootstock is so vigorous, it pushes a lot of growth upward.
Without pruning, you might end up with a tangled mess of branches that’s hard to support and prone to disease.
By selectively removing suckers, you’re teaching the plant to focus its energy on a few main stems that will produce large, healthy fruit.
3. Better Airflow Means Fewer Diseases
Grafted tomatoes are often chosen because they resist soil-borne diseases, but they can still get foliar diseases like blight.
When you prune grafted tomatoes, you open up the canopy so air can circulate freely.
This dries the leaves faster after rain or watering, which dramatically reduces the chance of fungal issues.
So pruning isn’t just about size, it’s about keeping your grafted tomato plant healthy all season long.
When to Start Pruning Grafted Tomatoes
You should start pruning grafted tomatoes about two to three weeks after transplanting them into your garden or large container.
At this point, the graft union should be well-healed, and the plant should be actively growing.
Don’t start pruning too early because the plant needs those leaves to establish a strong root system.
Wait until you see new growth on the scion that’s clearly above the graft line.
Then, you can begin your ongoing pruning routine for the rest of the season.
The Early Season Cleanup
The first time you prune grafted tomatoes, focus on the bottom of the plant.
Remove any leaves that are touching the soil, as these are prime entry points for soil-borne pathogens.
Also, remove any tiny suckers that are already forming in the leaf axils of the scion.
This initial cleanup sets the stage for good airflow and directs the plant’s early energy into establishing those main stems.
Step-by-Step: How to Prune Grafted Tomatoes Like a Pro
Let’s get into the actual mechanics of how to prune grafted tomatoes.
You’ll need a sharp pair of pruning shears or just your fingers for young, tender shoots.
The key is to be consistent and check your plants at least once a week.
1. Identify the Graft Union First
Before you make any cut, locate the graft union.
It looks like a swollen, knobby scar on the main stem, usually a few inches above the soil line.
Everything above that scar is your scion, and everything below is your rootstock.
You should never cut the graft union itself, as that can kill the plant.
2. Remove All Rootstock Shoots
Look at the stem below the graft union.
Any shoot emerging from there gets removed, period.
These are easy to spot because they often look more vigorous and may have slightly different leaf shapes.
Snap them off with your fingers or snip them close to the stem.
Don’t leave a stub, as that can invite disease.
3. Pinch Out the Suckers on the Scion
Now, move above the graft union.
Suckers are the shoots that grow in the crotch between the main stem and a branch.
For grafted tomatoes, you have two choices: single-stem pruning or double-stem pruning.
For most home gardeners, single-stem is easiest.
Just pinch out every sucker you see, leaving one main, vertical stem.
If you want two main stems, allow the first sucker below the first flower cluster to grow, then pinch out all the others.
4. Remove Lower Leaves Gradually
As your grafted tomato grows taller, the lower leaves on the scion will start to yellow.
Remove these leaves as they appear, especially the ones that are shaded or touching the ground.
This keeps the plant clean and improves airflow, which we talked about earlier.
5. Top the Plant at the End of the Season
About four to six weeks before your first expected frost, stop the plant from growing taller.
To do this, simply cut off the growing tip of the main stem.
This is called “topping,” and it forces the plant to put all its remaining energy into ripening the fruit that’s already set.
When you top a grafted tomato, you’re essentially telling it: no more new growth, just finish what you’ve started.
Common Mistakes When You Prune Grafted Tomatoes
Even experienced gardeners make mistakes when they prune grafted tomatoes.
Knowing what to avoid will save you a lot of heartache later on.
1. Pruning Too Aggressively
Don’t strip your plant bare.
Leaves are the plant’s food factory.
If you remove too many, especially on a hot day, you’ll stress the plant and sunscald the fruit.
A good rule of thumb is to never remove more than a third of the plant’s foliage at one time.
2. Ignoring the Rootstock Shoots
If you let rootstock shoots grow for more than a week, they can get thick and woody.
Removing them then will leave a large wound that’s slow to heal.
Stay on top of them by checking your grafted tomatoes every few days.
3. Pruning When the Plant Is Wet
Don’t prune grafted tomatoes when the leaves are wet from rain or morning dew.
Wet conditions make it super easy to spread bacterial diseases from one cut to another.
Wait until the afternoon when the plant is dry, and you’ll have a much healthier plant.
So, How Do You Prune Grafted Tomatoes for Maximum Yield?
You prune grafted tomatoes by focusing on the graft union, removing rootstock shoots without mercy, and keeping the scion to one or two main stems.
That’s the simple answer, but the execution is where the magic happens.
Consistency is your best friend.
When you prune grafted tomatoes weekly, you stay ahead of the growth, and the plant never has a chance to waste energy on unwanted shoots.
So get out there, find that graft union, and start snipping.
Your grafted tomato plants will thank you with a huge, delicious harvest.
Happy gardening, and enjoy the fruits of your labor.