Why and when to prune tomato plants
Pruning tomato plants increases yield by directing the plant's energy toward fruit instead of leaves and stems. A tomato plant that grows unchecked will produce many branches but fewer tomatoes per branch, and the fruit that does grow will be smaller and slower to ripen. Removing the right growth at the right time lets the plant focus on making larger, sweeter tomatoes in greater numbers.
The best time to start pruning is when the plant is 6 to 8 inches tall and has its first true leaves—the leaves that look like actual tomato leaves, not the smooth seed leaves that emerged first. Continue pruning throughout the growing season, removing growth as it appears. Stop pruning about 4 weeks before your first expected frost, so the plant can finish ripening the fruit already on the vine.
Key Takeaways
- Remove suckers (shoots that grow between the main stem and branches) on indeterminate varieties to keep the plant focused on fruit production rather than excessive foliage.
- Pinch off the bottom 6 to 8 inches of leaves once the plant is established, which improves air flow and reduces disease.
- Determinate (bush) tomatoes need minimal pruning—remove only dead leaves and the lowest branches; indeterminate (vining) varieties benefit from regular sucker removal.
- Use clean, sharp pruners or pinch off small growth by hand to avoid spreading disease between plants.
- Stop all pruning about a month before the first frost so the plant can ripen the fruit already developing.
The difference between determinate and indeterminate tomatoes
Determinate tomatoes (also called bush tomatoes) grow to a fixed height, usually 3 to 4 feet, and produce most of their fruit in a short window. Varieties like 'Roma' and 'San Marzano' are determinate. These plants need very little pruning—remove only dead or diseased leaves and the lowest branches that touch the soil, which keeps disease spores from splashing up.
Indeterminate tomatoes (vining varieties) keep growing taller throughout the season and produce fruit continuously until frost. 'Brandywine', 'Cherokee Purple', and 'Sungold' are indeterminate. These are the plants that benefit most from regular pruning, because they will grow 6 feet tall or taller if left alone, and all that extra growth uses energy that could go into fruit.
How to remove suckers without harming the plant
A sucker is a shoot that grows in the angle (called the axil) between the main stem and a branch. Suckers look like small stems with leaves, and they will grow into full branches if left alone. On indeterminate varieties, removing suckers is the single most important pruning task. On determinate varieties, you can leave them alone.
Pinch off suckers when they are 2 to 4 inches long, before they become woody. Use your thumb and forefinger to snap them off, or use clean pruners if the sucker is thick. The best time is early morning when the plant is firm and full of water. If you wait until the sucker is 12 inches long and thick, removing it will stress the plant more than if you had pinched it off weeks earlier.
Do not remove the main stem or the primary branches—only the growth that sprouts between them. If you are unsure whether a shoot is a sucker or a branch, leave it alone for a few days and watch where it grows. A sucker will grow straight up from the axil; a branch grows from the main stem itself.
Removing lower leaves to prevent disease
Once your tomato plant is 12 to 18 inches tall and has several branches, remove all leaves from the bottom 6 to 8 inches of the stem. These lower leaves are the first to touch soil splash during rain or watering, and soil splash carries fungal spores that cause early blight and septoria leaf spot. Removing them stops the disease before it starts.
As the plant grows taller, continue removing leaves from the bottom as the plant adds height. By mid-season, you should have a clear stem with no leaves for the bottom 12 inches or more. This also improves air flow around the base of the plant, which dries the leaves faster after rain and further reduces disease risk.
Remove only leaves, not branches. Use clean pruners or pinch the leaf stem where it meets the main stem. Wash your hands or wipe your pruners with a cloth dampened in rubbing alcohol between plants to avoid spreading disease.
Thinning branches and leaves for better air flow
If your indeterminate tomato plant becomes very dense with foliage, thin out some of the inner branches and leaves so light and air can reach the center of the plant. Dense foliage traps moisture, which encourages fungal disease. Thin growth in early morning on a dry day so the cuts dry quickly.
Remove branches that are crossing or rubbing against each other, and remove leaves that shade developing fruit. You want sunlight to reach the tomatoes so they ripen fully and develop flavor. However, do not strip the plant bare—leaves feed the plant and protect fruit from sunscald (a white or yellow patch where the sun burns the skin). Aim for a balance where you can see into the plant but it still has plenty of foliage.
Topping the plant to speed ripening in late season
About 4 weeks before your first expected frost, pinch off the top growing tip of indeterminate tomatoes. This is called topping. The plant will stop growing taller and will redirect its energy into ripening the fruit already on the vine instead of making new flowers that will not have time to mature.
Topping is optional and works best in areas with a short growing season. In warm climates with a long season, topping is not necessary—the plant will produce fruit until frost anyway. If you do top, do it only once, about a month before the expected first frost date for your area.
Tools and hygiene to avoid spreading disease
Use sharp pruners that make a clean cut, not a crush. Dull pruners tear the plant tissue, which invites disease. Hand pruners work well for small suckers and leaves. Loppers (long-handled pruners) are useful for thicker branches. Bypass pruners, which work like scissors, are better than anvil pruners, which crush the stem.
Clean your pruners before you start and between plants. Wipe the blades with a cloth dampened in rubbing alcohol, or dip them in a 10 percent bleach solution (1 part bleach to 9 parts water) for 30 seconds, then rinse with water. Dirty pruners can spread early blight, septoria leaf spot, and other fungal diseases from one plant to another.
Wash your hands after pruning, and do not handle wet tomato plants—fungal spores spread more easily on wet foliage. Prune on a dry day or wait until the morning dew has dried.
Frequently Asked Questions
Can I prune tomato plants in the rain or when they are wet?
No. Wet foliage spreads fungal spores more easily, and wet cuts heal more slowly. Prune on a dry day, or wait until morning dew has dried. If you must prune a wet plant, clean your pruners between every cut to avoid spreading disease.
What should I do with the leaves and branches I remove?
Do not compost them if they show any sign of disease (spots, yellowing, wilting). Throw diseased growth in the trash. Healthy leaves and small branches can go in a compost pile if it reaches 140°F, which kills most pathogens. If you are unsure, throw them away to be safe.
Will pruning reduce my harvest?
No. Proper pruning increases yield by directing the plant's energy toward fruit instead of excessive foliage. Removing suckers and lower leaves on indeterminate varieties will give you larger, riper tomatoes in greater numbers than an unpruned plant.
How much can I prune without hurting the plant?
Remove suckers and lower leaves freely. For branch thinning, remove no more than one-third of the foliage at a time. If you remove too much at once, the plant will be stressed and may stop producing fruit temporarily. Prune gradually throughout the season rather than all at once.
Do I need to prune cherry tomatoes?
Cherry tomatoes are usually indeterminate and will grow very tall if left alone, so they benefit from sucker removal and lower leaf removal just like larger indeterminate varieties. However, they are more forgiving of heavy pruning and will still produce well even if you prune lightly or not at all.