How To Prune Tomato Plants

If you fastidiously check on your tomato plants more than once a day, you probably already know that pruning can be an important part of your plant care routine. Pruning tomato plants is an optional, yet recommended, technique that some gardeners use to keep plants tidy, manipulate fruit size, and even hasten their ripening. Before we discuss how to prune tomato plants, it's important to understand which types of tomato plants you should prune and why.

Why You Should Prune Tomatoes

While pruning isn’t required for tomato plants, some gardeners prune them to improve production. If you prune your tomato plants, make sure they are indeterminate varieties, which continue to grow all season long and may benefit from regular maintenance. Pruning helps the plant focus on the fruit instead of putting its energy into growing more leaves.

Improved Airflow

Fewer leaves mean the plant is less dense, which allows for more air to flow among the stems. Pruning removes leaves on the ground that may be in constant shade and in contact with wet soil, which can lead to disease. A well-pruned plant will also dry faster after a rain, so they are less susceptible to diseases that develop from prolonged moisture, humid weather, and poor air circulation.

Fungal, bacterial, and viral diseases can all infect tomato plants. Among the most common, and perhaps the most detrimental, is late blight, caused by the Phytophthora infestans fungus. It can kill the entire plant and is highly contagious, spreading by releasing spores into the wind. Other diseases to read up on and look out for include early blight, southern blight, fusarium wilt, buckeye rot, blossom end rot, septoria leaf spot, gray wall, anthracnose, verticillium wilt, and bacterial speck.

Fewer leaves also make it easier to spot insect pests that like to hide in thick canopies of leaves. Common enemies of tomato plants are aphids, hornworms, thrips, whiteflies, tomato psyllids, fruitworms, and flea beetles.

Bigger Fruit

Pruning at the right time directs the plant's energy toward its best growth, creating and ripening fruit instead of making more leaves. Overall, you will probably have less fruit on a pruned plant, but the fruit will ultimately grow to be bigger. And, since pruned plants can be put a bit closer together in the ground because the growth is so vertical, you can have more overall plants in your home garden. When a plant has fewer leaves and less fruit to take care of, that fruit ripens faster. This can help in short-season climates, where getting a tomato harvest is often a race against time, thanks to early fall frosts.

Size Control

Pruning can help keep the size under control, especially for container plants. Choose compact varieties to grow in containers to keep their size in check. Removing the suckers gets rid of any extra foliage that can cause a tomato plant to outgrow its space. Then there's more room for other tomato plants.

Determinate vs. Indeterminate Tomatoes

When you purchase a tomato plant from a nursery, the container label should identify the plant as either determinate or indeterminate.

Determinate tomato varieties are often referred to as "bush" tomatoes because they do not continue extending in length throughout the season. Growing a determinate variety, such as Roma, is practical when you want a lot of tomatoes at one time for freezing or canning and are ideal for making tomato sauces. Determinate tomatoes do not need to be pruned. Because they develop all of their fruit at one time, pruning may cause you to sacrifice tomatoes for no reason.

Indeterminate tomato varieties, such as Beefsteak and Brandywine, are vining plants that continue to extend in length and produce fruit throughout the growing season. Pruning indeterminates can help to keep the huge vines in control and encourage the plants to produce tomatoes large enough for your classic BLT sandwich or tomato pie, instead of lots of foliage and many smaller tomatoes. Many cherry tomato varieties are indeterminate as well, and proper pruning will guarantee clusters of tomatoes throughout the entire season.

When To Prune Tomatoes

Prune tomato plants during the early morning, and make sure the plants are dry. If they are wet from rain, dew, or sprinklers, give them time to dry. Prune your tomato plant when the suckers are two to four inches long so the plant won’t spend energy growing new branches off of the main ones. Prune indeterminate tomatoes every couple of weeks as they continue to grow.

How To Prune Tomatoes

Pruning is really a simple process. The first pruning should be done when you first plant your tomatoes. Remove any lower leaves that will rest on the ground once planted, and pinch off any flowers on the plant until it reaches about 12 to 18 inches tall so the plant can focus on growth while it’s young. To prune during the growing season, simply remove the suckers. Here's how:

1. Look for the tomato "suckers," which are the side shoots that grow in the "V" space between the main stem and the main branches on your plant. If left alone, these suckers will eventually grow into full-sized branches—adding lots of foliage and, eventually, a few fruits. This will also result in a tomato plant that quickly outgrows its space in the garden. If they are under 2 inches long, you can pinch the sucker off with your fingers, but use a pair of clean gardening pruners for larger ones.
2. Always disinfect your pruners with bleach as you move from one plant to another to prevent the spread of disease. Keep an eye on your tomato plants so you can remove suckers as they emerge. Removing large amounts of foliage at once can be stressful for the plant.
3. Stake up or remove any branches that are low-hanging or touching the ground; foliage that is touching the ground can be susceptible to many of the aforementioned bacteria, fungi, and viral infections that can spread through the rest of the plant.

Common Pruning Mistakes

To avoid adding stress to your plant or introducing harmful bacteria, here's what to avoid when pruning to get the most out of your plants.

• Using dirty tools can introduce bacteria and fungi. Clean your tools with rubbing alcohol or bleach after use on each plant.
• Pruning too many leaves at one time can stress the plant. Remove any yellow leaves, lower leaves, and suckers to boost the plant’s health.
• Pruning wet plants may encourage the spread of bacteria or fungi that can harm your plant. Wait until the plant is dry before pruning.
• Pruning determinate plants will reduce their yield. Prune only indeterminate tomato plants.
• Waiting too long to remove suckers means the plant spends energy on unnecessary growth that could be spent on the fruit.