Can Indeterminate Tomatoes Be Pruned to Reduce Size?

Support

• Indeterminate tomatoes require support to hold the stems upright and to allow for proper pruning. Stakes must measure at least 6 feet tall to properly support an indeterminate tomato. As the plant grows, you tie the main stems to the stake loosely with cloth ties. Generally, you begin tying after the tomato produces its first flower cluster and then space the subsequent ties at 8-inch intervals. You must prune out the extra stems that form so the plant doesn't grow too large for the support and to encourage good fruit set.

Early Sucker Removal

• Suckers form at the juncture between a leaf and a main upright stem. These small side shoots pose the greatest problem when they form beneath the stem supporting the first flower cluster. The lower they are on the stem, the stronger the sucker. These lower suckers can develop into new main stems, which weaken the plant while making it large and unwieldy. You can pinch off the suckers with your fingers when the sucker grows to a 3-inch length. You can allow one or two to grow into new stems if desired, but any additional stems only weaken your tomato plant.

Maintenance Pruning

• As the plant becomes larger in late summer, it produces suckers above the first flower cluster. The suckers usually don't develop into main stems, but they can make you plant overly large for the space or support. Pinch off these suckers at any time after they grow to a 3-inch length to help limit the spread of the bush. Removing suckers close to the tip of the stem can also slow upward growth if the plant is becoming too tall for its location.

Topping

• In late summer or fall you may need to top the plant to control size or to force tomato ripening before frost. Pinch off the growing tip of the main stems to the topmost leaf to slow upward growth when the plant starts to overgrow its support. About 30 days before the first fall frost, you can pinch back all the remaining side stems in the same manner. This forces the tomato to quit flowering while allowing the remaining fruits to reach full maturity more quickly.