How to Prune Tomato Plants

Pruning tomato plants is a simple yet effective way to boost growth, increase fruit production and maintain a tidy garden. Whether you're growing in a greenhouse or outdoors, proper pruning helps direct the plant’s energy where it matters most — into producing strong, healthy tomatoes. The technique you use depends on the type of tomato you're growing: indeterminate varieties need regular pruning, while determinate ones typically do not.

Why You Should Prune Tomato Plants

Pruning helps tomato plants stay focused on producing fruit instead of growing excess foliage. It improves airflow around the plant, reducing the risk of diseases like blight and mould. It also makes harvesting easier and ensures that sunlight can reach the developing fruits. For indeterminate varieties, pruning keeps the plant manageable and encourages earlier ripening of fruit.

When to Prune Tomatoes

Start pruning once the plant is established and has begun to develop strong vertical growth. This usually happens a few weeks after transplanting. Regular weekly checks are ideal. The best time of day to prune is in the morning on a dry day, allowing cuts to heal quickly. Avoid heavy pruning in the late stages of growth, as it can slow down fruit development.

Things to Avoid When Pruning Tomatoes

Never remove too much foliage at once. While it’s tempting to strip the plant down for a cleaner look, tomatoes rely on their leaves to photosynthesise and produce sugars for fruit development. Avoid cutting main stems or over-pruning lower leaves too early. Also, don’t use blunt or dirty tools — this can lead to infection.

Can I Prune My Tomato Plant When It Is Wet?

Avoid pruning when the plant is wet. Moisture on the leaves and stems creates ideal conditions for disease to spread through open cuts. Always wait for a dry period before pruning, even if the task feels overdue. Clean cuts made in dry conditions reduce the risk of bacterial or fungal problems significantly.

Should I Prune My Tomato Plants When They Are Fruiting or Flowering?

Yes, light pruning can continue during flowering and fruiting, but it needs to be strategic. Remove suckers — the shoots that grow between the main stem and branches — to keep energy focused on existing flowers and fruits. Don’t prune flowering stems or fruit-bearing branches. The goal is to manage foliage, not disrupt production.

Common Mistakes to Avoid When Pruning Tomato Plants

A few common mistakes can set back your tomato crop. One is confusing suckers with main stems — suckers are smaller and grow from leaf joints, while main stems are thicker and form the core structure. Another is over-pruning, especially during hot weather, which can lead to sunscald on exposed fruit. Finally, neglecting pruning altogether can result in tangled, overgrown plants with fewer and smaller tomatoes.

Know Your Tomato Type: Determinate vs Indeterminate

This is the foundation of pruning tomatoes correctly.

• Determinate varieties (also called bush tomatoes) grow to a fixed size, flower all at once, and then stop. They don’t need pruning — in fact, removing suckers or growth can reduce your yield.

• Indeterminate varieties keep growing and producing throughout the season. These are the ones that benefit most from consistent pruning to manage growth and maximise fruit.

Target the Suckers, But Don’t Strip the Plant

Suckers grow in the “V” between the main stem and a branch. If left unchecked, each sucker can become a full branch, which leads to a crowded, leafy plant. Pinching off small suckers early is best — they come off cleanly by hand and the plant doesn’t waste energy on them. That said, some growers keep a few strong suckers to form secondary stems for a two-leader or three-leader training system.

Lower Leaf Removal for Disease Prevention

Once fruit begins forming, especially on the lower trusses, you can begin removing the lowest leaves on the plant — particularly any yellowing or damaged ones. This improves air circulation at the base, reduces splash-up from soil (a common source of disease), and keeps the plant tidy.

Tip Pruning for the End of Season

As the season winds down, pruning the top of an indeterminate tomato plant (called “topping”) can help. By cutting off the growing tip a few weeks before the first expected frost, the plant stops producing new flowers and focuses on ripening the fruit it already has.

Don’t Forget to Support Your Pruning

Pruned plants need good support. Pruning helps focus the plant's energy, but without solid staking or a trellis system, even a well-pruned tomato can droop or snap under the weight of its fruit. Tie the plant in loosely with soft ties and adjust as it grows.

A Little Stress Isn’t a Bad Thing

Pruning creates minor stress for the plant, which often results in improved fruit quality — more flavour and sweetness. That’s because the plant channels its sugars into fewer fruits rather than spreading them across excess growth.