Should I Prune Tomato Suckers? Why It Matters and How to Do It

Yes, you should prune tomato suckers — but only on indeterminate varieties.

Removing suckers from indeterminate tomatoes (like most heirloom and many hybrid varieties) directs the plant's energy toward ripening fruit rather than growing additional stems.

For determinate varieties, pruning suckers is counterproductive and can reduce your harvest.
Knowing which type you're growing is the essential first step.

What Is a Tomato Sucker?

A tomato sucker is a shoot that emerges from the axil — the V-shaped junction between the main stem and a lateral branch.

Left unpruned, a sucker will grow into a fully functional stem with its own leaves, flowers, and eventually fruit.

In an indeterminate plant that keeps growing all season, this branching multiplies rapidly, and the plant can easily develop into an unmanageable tangle of stems competing for the same root system's resources.

Suckers are not the same as leaves, flower trusses, or the main growing tip of the plant. They grow specifically from those axil points and have their own distinct upright growing pattern.

Indeterminate vs. Determinate: The Rule That Changes Everything

Before you pick up a pruner, you must know which type of tomato you're growing.
Indeterminate tomatoes grow continuously throughout the season, setting fruit over an extended period.
They can reach 6–10+ feet tall and produce suckers constantly.

Pruning these plants to 1–2 main stems is a widely practiced and evidence-supported technique for improving fruit size and ripening speed.
Common indeterminate varieties include most heirlooms (Cherokee Purple, Brandywine), many Beefsteak types, most cherry tomatoes (Sun Gold, Sweet 100), and many popular hybrids.

Determinate tomatoes are genetically programmed to grow to a set height, set a concentrated flush of fruit, and stop.

Their flower and fruit production is spread across all their stems — including suckers.

The University of Illinois Extension and UC Cooperative Extension both note that pruning suckers from determinate tomatoes removes potential fruiting wood and typically reduces total yield.

Common determinate varieties include Roma, San Marzano (many versions), Celebrity, and most paste tomatoes.

How to tell the difference: Check the seed packet or plant tag.

Indeterminate is often abbreviated as "I" or "V" (vining), determinate as "D" or "bush."

If you're unsure, contact the nursery or check the variety name online.

Why Prune Suckers on Indeterminate Tomatoes?

The principle is straightforward: a tomato plant has a fixed photosynthetic capacity at any given time. Every new stem the plant grows diverts carbohydrates, water, and nutrients away from existing fruit.
An unpruned indeterminate tomato will produce many smaller fruits over a longer period; a pruned one trained to 1–2 stems will produce fewer, larger, earlier-ripening fruits.
Research from the Royal Horticultural Society (RHS) confirms that single-stem training of indeterminate tomatoes under controlled conditions reliably produces larger individual fruit and earlier maturity compared to unpruned plants.
The trade-off is total fruit number — which is why some gardeners prefer a middle-ground approach of 2-stem training.

Additional benefits of sucker pruning on indeterminate varieties:

• Better airflow through the plant, reducing fungal disease risk (especially blight and botrytis)

• Easier staking and support

• Improved light penetration to ripening fruit

• More manageable plant size in small gardens or containers

Why You Should NOT Prune Determinate Tomatoes

Determinate varieties concentrate their fruit set across all growing tips — including those that would develop from suckers.

Removing suckers removes entire fruiting branches.

The result is a plant with fewer fruits and no benefit to ripening speed, since the variety is already genetically timed for a concentrated harvest window.

If your goal is canning, sauce-making, or preserving — common uses for Roma and San Marzano types — you want maximum fruit production from determinate plants, which means leaving all suckers intact and focusing instead on adequate watering and soil nutrition.

How to Identify Suckers (and Distinguish Them from Stems)

Look for the V-shaped axil between the main stem and any lateral branch. A sucker is the new growth emerging from that precise junction. It will have a slightly different, more upright angle than the branch below it and will be smaller and more tender than established stems.

Easy identification tips:

• Suckers emerge from axils, not from the main stem directly or from leaves

• New suckers are often a brighter, slightly yellowish-green

• A sucker will have a small but identifiable growing tip within days of emergence

• If you're unsure whether it's a sucker or a branch, trace it back to its origin point — if it's coming from an axil, it's a sucker

Which Suckers to Keep

Not all suckers should be removed, even on indeterminate varieties.

The most important sucker to consider keeping is the first sucker below the first flower cluster.

This sucker, once established, becomes a strong second main stem and can significantly increase productivity without creating the overly bushy problems of leaving all suckers.

In two-stem training — a method widely used by experienced home gardeners and documented by Cornell University's vegetable extension programs — you keep exactly this sucker and remove all others.

The result is a plant with two main fruiting stems, good airflow, and a manageable structure.

Suckers that emerge very close to the soil (within the lowest 6–8 inches of the main stem) should always be removed, as they are vulnerable to soil-borne pathogens and can serve as entry points for disease.

Step-by-Step: How to Remove Tomato Suckers

Small suckers (under 2 inches):

1. Locate the sucker in the axil of the branch

2. Pinch firmly between your thumb and forefinger

3. Snap or twist the sucker cleanly off

4. No tool needed; clean breaks heal fastest

Larger suckers (over 2 inches):

1. Use a clean, sharp pair of pruning scissors or a single-edge razor blade

2. Sterilize the blade with isopropyl alcohol or a 10% bleach solution before each plant to prevent disease transmission

3. Cut cleanly at the base of the sucker, as close to the main stem as possible without nicking it

4. Allow the wound to air-dry; do not apply wound sealant (evidence does not support this practice for tomatoes)

Best time to prune: Early morning on a dry day. This gives the cut surface time to dry and seal before the evening humidity that favors fungal pathogens.

Post-Pruning Care: Compost Mulch and Recovery

After a pruning session, support your plants' recovery and ongoing health with a 2–3 inch layer of finished compost mulch around the base of each plant (keeping a 2-inch gap from the stem itself).

Compost mulch does several things simultaneously:

• Feeds the root zone as it breaks down, providing steady nitrogen and micronutrients exactly when plants need them for fruit development

• Retains soil moisture, which is critical for calcium uptake and preventing blossom end rot — a common post-pruning issue if plants experience moisture stress

• Regulates soil temperature, protecting roots from heat stress during summer months

• Suppresses weeds that would otherwise compete for nutrients The combination of proper sucker pruning and consistent compost mulching is, according to the Rodale Institute, one of the most effective organic management strategies for high-quality tomato production.

Common Pruning Mistakes to Avoid

• Pruning determinate varieties — the most common and most costly mistake

• Removing the main growing tip — this effectively stops the plant's upward growth and is irreversible

• Using dirty tools — transfers bacteria and fungal spores between plants; always sterilize

• Pruning in wet conditions — increases disease pressure at wound sites

• Waiting too long — large suckers are harder to remove cleanly, leave bigger wounds, and have already consumed significant plant resources

• Removing all suckers from an indeterminate plant at once — sudden defoliation stresses the plant; if a plant is heavily suckered, spread removal over several days

Practical Takeaways

• Confirm whether your tomato is indeterminate (prune suckers) or determinate (leave suckers) before doing anything

• For indeterminate types, train to 1–2 stems by removing all suckers except, optionally, the first one below the first flower cluster

• Pinch suckers when small (under 2 inches) for cleanest removal; use sterilized scissors for larger ones

• Always prune in the morning on dry days

• Follow pruning with compost mulch at the base to support recovery, moisture retention, and steady feeding

Frequently Asked Questions

Q: Will my tomatoes produce fewer fruits if I prune suckers?

A: On indeterminate varieties, you will likely get fewer but larger, earlier-ripening fruits. Total weight can be similar or higher on a per-plant basis with good management. On determinate varieties, pruning will reduce fruit production.

Q: Can I root the suckers I remove and grow new plants?

A: Yes. Tomato suckers are easy to root. Place them in water or moist potting mix, keep in indirect light for 1–2 weeks, and transplant when roots are 1–2 inches long. This is a free way to expand your garden.

Q: What happens if I never prune tomato suckers?

A: On indeterminate varieties, the plant becomes very large, bushy, and difficult to support. You'll get plenty of tomatoes, but they'll be smaller, later to ripen, and the plant will be more susceptible to fungal disease due to poor airflow.

Q: How often should I check for new suckers?

A: During peak growing season (warm weather), new suckers emerge every 5–7 days. A quick weekly walk-through your tomato plants to pinch new suckers is a good habit.

Q: Is it too late to start pruning if my plants are already large?

A: You can still prune, but be gradual. Remove the largest, most problematic suckers first and space removal over a week to reduce plant stress. It will still improve airflow and help redirect energy, even if you didn't start at planting.

References

• Cornell University Vegetable Extension. (2023). Tomato Production in the Home Garden.

• Rodale Institute. Organic Tomato Production.

• Royal Horticultural Society (RHS). Growing Tomatoes.

• UC Cooperative Extension. (2022). Tomatoes in the Home Garden.

• University of Illinois Extension. Tomatoes.

• USDA NRCS. Soil Health and Vegetable Production.

Author bio: [Reencle Content Team — passionate about sustainable food systems, soil health, and making composting accessible for every household. Content reviewed by horticultural and environmental science advisors.]