How to Prune Tomato Plants

When cultivating tomatoes, your primary goal is usually to harvest as many ripe fruits as possible. If you're growing indeterminate or "vining" tomato varieties (such as Big Boy, Beef Master, and most heirloom types), it's essential to prune unnecessary shoots and leaves to help the plant focus its nutrients on fruit production. However, excessive pruning can be counterproductive for determinate varieties (like Biltmore, Heinz, and Patio).

Identify the type of tomato plant you are growing. Before pruning, you need to know whether your tomato plant is indeterminate or determinate. Indeterminate varieties grow like vines, require staking or trellising, and need regular pruning for optimal growth. Determinate varieties grow as bushes, naturally directing nutrients to fruit production without much intervention. Here are some common varieties for each type:

• Indeterminate varieties: Big Boy, Beef Master, Black Prince, German Queen, most cherry tomatoes, and heirloom varieties.
• Determinate varieties: Ace 55, Amelia, Better Bush, Biltmore, Heatmaster, Heinz Classic, Mountain Pride, and Patio.

Check for yellowing leaves. A clear sign that it’s time to start pruning is when the leaves below the first flower cluster begin to turn yellow. Once you notice this, you can begin pruning your plant.

Inspect the side shoots. Look for tiny new shoots growing where the branches meet the main stem of indeterminate tomato plants. These are called “suckers” and should be removed. Leaving them intact will drain nutrients from the rest of the plant, reducing fruit production. While not always harmful, removing these shoots encourages larger fruit throughout the season.

Look for tomato flowers. You should start pruning your tomato plant early, as soon as it begins to flower. At this stage, the plant is typically around 30–45 cm tall.

Remove all suckers and leaves below the first flower cluster. This should be done regardless of the tomato variety you’re growing. It strengthens the plant by allowing the main stem to grow sturdier. When suckers are removed, most nutrients are directed toward fruit production rather than wasted on unnecessary growth.

• To remove suckers, pinch them off with your fingers by bending them back and forth until they snap off cleanly. This is easiest when the suckers are young and tender. The small wound will heal quickly. This method is called “simple pruning.”
• For branches and leaves (not suckers) below the first flower cluster: If you’re in a warm climate, such as zone 9, wait until the leaves turn yellow. They help shade the ground until the plant matures. Conversely, if growing in a humid environment (like a greenhouse), prune everything below the first flower cluster to improve airflow. Humidity can promote disease, slow the healing of pruning wounds, and make the plant more vulnerable. Enhancing ventilation can protect the plant.

Leave robust suckers intact. Avoid removing thick suckers, as this can harm the entire plant. If the suckers are thicker than a pencil, use the “Missouri pruning” method, which involves trimming only the tips of the suckers and leaving 1-2 leaves for photosynthesis and to protect developing fruits from sunburn. The downside is that new suckers will grow from the remaining stem, requiring additional pruning. This technique is ideal for handling large suckers; if the cut becomes diseased, it will be farther from the main stem. This method also minimizes shock to the plant.

• Prune suckers throughout the summer to maintain plant health. These shoots grow quickly, so you may need to prune them 1-2 times a week.

For indeterminate tomato varieties, keep only 4-5 fruit-bearing flower clusters and remove the rest. These are the branches growing above the first flower cluster. Retaining 4-5 clusters will produce large, healthy fruits, but more than that will result in smaller and fewer fruits. Select 4-5 strong clusters to keep and remove all other suckers, leaving only the main stem, also known as the terminal shoot.

• Ensure vining tomato varieties are staked after flowering. Otherwise, the vines will sprawl on the ground and fail to produce healthy fruits.
• Determinate tomato varieties have a limited number of branches and grow naturally, so they don’t require pruning above the flower cluster. Pruning them excessively may remove fruit-bearing branches instead of aiding fruit production.

Remove yellow leaves. Yellow leaves consume more sugar than they produce. As the plant matures, the lower leaves will naturally turn yellow and wither. This is completely normal; simply pluck off the yellow leaves as they appear. This keeps the plant vibrant and helps prevent disease.

Top the plant. For the best harvest at the end of the growing season, you need to “top” the plant. About a month before the first expected frost or when the plant reaches the top of the greenhouse, remove the terminal shoot. By this point in the season, developing tomatoes have little time to ripen, so all nutrients must be directed straight to the fruit.