Pruning and training tomatoes
Manage indeterminate and determinate tomatoes through pruning, suckering, and support systems that improve airflow and fruit quality.
11 min · intermediate
You will learn
- Distinguish indeterminate and determinate growth habits
- Identify and manage tomato suckers
- Train indeterminate tomatoes to a single trunk
Indeterminate vs. determinate
Colorado State University Extension describes indeterminate tomatoes as continuing to flower and bear fruit until frost, typically needing staking or caging. Determinate types stop vine growth when flowering begins and put on a concentrated crop with less need for sucker removal. Know your variety before pruning; removing growth from determinate plants can reduce yield.
Understanding suckers
Suckers are shoots that emerge from the joint between the main stem and a leaf branch. On indeterminate plants, suckers become additional stems that flower and fruit. Each stem diverts energy; more stems mean more fruit but smaller size and denser foliage. In humid climates, dense growth increases disease risk.
Single-stem training
Colorado State University Extension recommends training indeterminate tomatoes to a single trunk by removing suckers below the first flower cluster. This produces fewer but larger fruit and excellent airflow. Pinch suckers when they are small, ideally on a dry morning. Disinfect tools between plants if disease is present.
Support and lower leaf removal
Stake, cage, or trellis plants before they need it to avoid breaking branches. Tie stems loosely with soft material as they grow. Remove lower leaves that touch soil to reduce splash-borne disease. Prune only during dry weather and stop heavy pruning several weeks before expected first frost so plants can set and ripen remaining fruit.