Prune tomato plants in early summer when they are 12 to 18 inches tall, and continue removing shoots every one to two weeks until late summer

Pruning tomato plants means removing shoots, leaves, and branches to direct the plant's energy toward fruit instead of foliage. The timing and method depend on whether you grow determinate (bush) or indeterminate (vining) varieties. Indeterminate tomatoes benefit most from pruning because they grow continuously throughout the season. Determinate varieties produce most of their fruit at once and need little to no pruning.

Start pruning when the plant reaches 12 to 18 inches tall, usually four to six weeks after planting. At that point, the plant is established enough to handle the stress. Continue pruning every one to two weeks through late summer—usually mid-August in most regions—to avoid stimulating new growth that won't have time to mature before frost.

Key Takeaways

  • Indeterminate tomatoes should be pruned regularly; determinate (bush) varieties need little or no pruning.
  • Remove suckers—shoots that grow between the main stem and branches—by pinching them off by hand when they are small.
  • Prune lower leaves once fruit sets to improve air circulation and reduce disease.
  • Stop pruning in late summer so the plant can focus energy on ripening existing fruit before frost.
  • Use clean hands or pruners to avoid spreading disease between plants.

What suckers are and why you remove them

A sucker is a shoot that grows from the joint where a branch meets the main stem. It looks like a small stem with leaves sprouting at a 45-degree angle. If left alone, suckers grow into full branches that produce leaves and flowers but divert energy away from fruit development. On an indeterminate plant, removing suckers keeps the plant focused on ripening fewer, larger tomatoes instead of spreading itself thin across many small ones.

Pinch off suckers when they are 1 to 2 inches long by using your thumb and forefinger to snap them off. This is easier and less stressful to the plant than waiting until they are woody and require pruners. Check the plant every few days during the growing season because new suckers appear constantly on indeterminate varieties.

Do not remove all the leaves along with the sucker. Leave the main stem and the branch it grows from intact. The goal is to remove only the sucker itself.

Removing lower leaves to prevent disease

Once the plant begins setting fruit—usually when the first flower cluster has small green tomatoes—start removing the lowest leaves on the stem, working your way up. Remove leaves that touch the soil or hang below the first fruit cluster. These leaves are most likely to pick up soil-borne diseases like early blight and septoria leaf spot, which splash onto leaves during watering.

Remove no more than one-third of the plant's leaves at a time. The leaves feed the plant and produce the sugars that make tomatoes taste better. Removing too many at once stresses the plant and can sunscald the fruit if the remaining leaves cannot shade it.

Use clean pruners or your hands to remove leaves. If you move between plants, wipe your pruners with a cloth dampened in rubbing alcohol or a 10 percent bleach solution (one part bleach to nine parts water) to avoid spreading disease.

When to stop pruning and why

Stop all pruning by mid-August in most regions, or about six weeks before your first expected frost date. At that point, the plant should focus every bit of energy on ripening the fruit already on the vine rather than growing new shoots and leaves. Pruning late in the season stimulates new growth that will not mature before cold weather arrives.

If you live in a warm climate where frost does not arrive until October or November, you can prune longer, but always stop at least six weeks before your frost date. Check your local frost date through your county extension office or a frost date calculator online.

Pruning determinate (bush) tomatoes

Determinate tomatoes grow to a set height—usually 3 to 4 feet—and produce most of their fruit within a short window, often two to three weeks. Because they are naturally compact and their fruit ripens all at once, they do not need the aggressive pruning that indeterminate varieties do.

For determinate plants, remove only dead leaves, diseased leaves, and any branches that touch the ground. You can remove a few lower leaves to improve air circulation, but do not remove suckers or prune the main stem. The plant needs all its foliage to support the heavy fruit load it produces at once.

Tools and technique for clean pruning

For small suckers and tender new growth, use your fingers. Pinch the sucker off between your thumb and forefinger with a quick, firm motion. This causes less damage than pruners on young growth and is faster when you are checking the plant every few days.

For larger branches, thicker stems, or leaves, use bypass pruners—the kind with two blades that pass each other like scissors. Anvil pruners (one blade pressing down onto a flat surface) crush the stem and leave a ragged cut that invites disease. Make cuts just above a leaf node or branch junction, angling the cut away from the remaining stem so water runs off instead of pooling.

Clean your pruners before moving to the next plant. Wipe the blades with a cloth dampened in rubbing alcohol or a 10 percent bleach solution. This takes 10 seconds and prevents spreading early blight, septoria leaf spot, and other fungal diseases from one plant to another.

Signs you are pruning too much

If the plant looks bare or you can see the main stem clearly through the foliage, you have removed too many leaves. The plant needs leaves to produce energy. Excessive pruning also exposes fruit to direct sun, which can cause sunscald—a pale, papery patch on the side of the tomato facing the sun.

If you notice sunscald appearing, stop pruning when ready and let the remaining leaves grow back. In future seasons, remove leaves more gradually and never remove more than one-third of the foliage at one time. Remember that the goal is to improve air circulation and reduce disease, not to strip the plant bare.

Frequently Asked Questions

Should I prune my tomato plant if it is already flowering?

Yes. Prune indeterminate plants even after they begin flowering. Remove suckers and lower leaves as usual. However, be gentler with the plant once it is in heavy flower or early fruit stage—avoid removing large sections of foliage at once, as the plant is already stressed from producing fruit.

Can I prune tomato plants on a rainy day?

Avoid pruning when the plant is wet or when ready after rain. Wet foliage spreads fungal spores more easily. Wait until the leaves are dry, usually a few hours after rain or watering. This also makes the work easier because wet stems are slippery and harder to pinch off cleanly.

What do I do with the leaves and suckers I remove?

Do not compost diseased leaves or leaves from plants with blight or leaf spot. Throw them in the trash. Healthy leaves and suckers can go in a compost bin if you have one, or in yard waste. Do not leave them on the ground near the plant, as they can harbor disease.

Will pruning reduce my tomato harvest?

On indeterminate plants, pruning usually increases harvest by directing energy toward fewer, larger, better-ripened tomatoes instead of many small ones. On determinate plants, pruning can reduce harvest if you remove too much foliage, so prune lightly or not at all on bush varieties.

Can I prune suckers from the bottom of the plant if it is already tall?

Yes. You can prune suckers from anywhere on the plant at any time during the growing season, as long as you stop six weeks before your frost date. Lower suckers are often easier to reach and remove early, so check the base of the plant regularly.