By Kathryn Hamilton, NC State Extension Master GardenerSM volunteer of Durham County
Behold the star of the 2026 Tomato Trial: the striking Pink Berkeley Tie-Dye slicer with its port-red and olive-green stripes. Growers and tomato lovers alike know that its good looks are second only to its complex flavor. It was also the variety used in our first tomato trial, testing grafted against ungrafted tomatoes, and we thought the comparison might be interesting. (Image credit: Kathryn Hamilton)
Exactly one month after we planted 40 Pink Berkeley Tie-Dye tomatoes for this year’s tomato trials, members of the tomato team watched in shock and awe as Durham County Extension Agent and project leader, Ashley Troth, pruned every plant to a single leader removing an average of 30% to 50% of the plant. “I’d rather hurt your feelings than the plant’s,” she said. “In the end, we’ll have bigger tomatoes, and more importantly, healthier plants.”
In this year’s project we are comparing three different root treatments to test their effectiveness on both production and longevity. The results will be compared both to an earlier trial where grafted tomatoes out-performed un-grafted, and to our “control” tomatoes which did not receive a root treatment.
Individual identification tags for each of the 40 Pink Berkeley Tie-Dye tomatoes in our trial. Tomatoes, we’ve got your number! (Image credit: Kathryn Hamilton)
Five beds were each planted with eight tomatoes. Each bed had one of the following root treatments:
- mycorrhizae1
- grafted root stock
- vermicompost2
- vermicompost and mycorrhizae
- no root treatment
All plants were fertilized with Tomato-tone® according to package directions.
The protocol is to grow each tomato on a single leader. And while the team regularly pruned suckers, we clearly weren’t aggressive enough as almost every tomato ended up with a sucker that turned into a double leader. Ashley gallantly picked up the shears. “When you prune to single leader you have fewer flowers, but this also gives each tomato fruit a chance to really grow. You also really open up the airflow through the plant, which helps decrease the chance of disease. While the poundage put out by the plant will be the same, it will come in fewer but bigger tomatoes, and many people appreciate the larger fruit.”
Single-Leader Pruning on Tomatoes
What Is It?
Every tomato starts with a single stalk, but as it grows, suckers – small new shoots that grow out of the “V” space where a horizontal branch joins the main vertical stem – grow. Unpruned, the sucker will grow into a full-sized main branch with tomatoes of its own, creating a dense plant.
Pink Berkeley Tie-Dye is a vigorous indeterminate cultivar, and the big fruit also requires a longer time to ripen. In this case single-leader pruning, especially in a congested garden, makes sense. While we often prune to two leaders when tomatoes are trellised, a single leader allows tomatoes that are tied to individual stakes as they grow to have increased air flow and therefore decreased disease pressure. (However, it is not advisable for determinate varieties on which tomatoes ripen over a short period of time.)
Why Do It?
- It creates a plant with only one “leader” or main branch that is easier to stake.
- It encourages the plant to create fewer, but larger tomatoes.
- It helps prevent fungal disease by increasing airflow.
How Is It Done?
Find the weaker of two leaders and prune. To avoid any cross-infection, sterilize your pruners between plants.
(Left to right) Extension agent and project leader Ashley Troth boldly cutting the weaker leader of the plant. Immediately, the plant looks more open. (Image credit: Kathryn Hamilton)
Identifying the Sucker
A tomato sucker is a small aggressive new shoot that grows in the “crotch” of a tomato plant where the horizontal leaf branch meets the main vertical stem. It grows out at a 45-degree angle. If left to develop, it will grow into a whole new branch capable of flowering and producing tomatoes.
(Left) Discerning a sucker from a new main branch can be challenging as seen here in a tomato plant in the trial that had the main branch accidentally cut. (Right) Detail of new sucker forming. (Image credit: Kathryn Hamilton)
The untrained eye can easily mistake a new main branch from a sucker as seen in this photo from our Tomato Trial. One month after the leader was accidentally trimmed, a new sucker has begun to form. It will eventually become the “leader.” But the severe pruning has definitely left the plant in a state of distress. We will follow this plant throughout the season.
The image below, clearly illustrates the difference between a sucker and new growth.
When pruning tomatoes, it’s critical to understand how to differentiate the main leader from a sucker. Pruning the main leader is not necessarily deadly but it can put the plant under stress. Production might also suffer. (Image credit: Kathryn Hamilton via Google Gemini)
And finally, a beauty shot of our new trimmed and slimmed tomatoes. (Image credit: Kathryn Hamilton)
Pruning isn’t just about aesthetics; it plays a major role in plant health. Disease resistance is the key to a plant’s longevity. Wet tomato leaves – from watering, rain, dew, or irrigation — are a breeding ground for fungal disease. Pruning creates better air circulation allows the leaves to dry to a point that reduces the environment for fungal spore germination.
If, like us, you have limited space and could use more “air” among your tomatoes, it’s not too late to create a single leader. It takes a bold heart. But you are likely to gain longer-lived plants and the bigger tomatoes that go with them.
Notes
1–Mycorrhizae are naturally occurring fungi in healthy soil, and they have a symbiotic relationship with the roots of many plants. These fungi absorb nutrients from the soil and transfers them to the plant. In return, host plant provides needed carbohydrates to the fungi. Home gardeners can purchase mycorrhizae amendments and even soil inoculated with the fungi.
2–Vermicompost is a nutrient-dense organic fertilizer and soil amendment that earthworms produce as they break down organic waste like yard trimmings and food scraps. You’ll often hear people refer to it as worm castings.
Resources and Additional Information
How to Achieve Peak Tomato Performance
Edited by Melinda Heigel and Susan Sharp, NC State Extension Master GardenerSM volunteers of Durham County
Article Short Link https://wp.me/p2nIr1-7Es
