How to Prune Tomato Plants
Some controversy exists over whether or not tomato plants should be pruned, and the reality is that if you don't, it will not necessarily cause problems. Plenty of people do not prune at all and still grow good tomatoes. Tomatoes are not one of those plants that require pruning or deadheading in order to survive, but shrewd pruning can improve the quality of the fruit you harvest.
Why You Should Prune Tomato Plants
The main reason to prune tomato plants is that it helps your plant direct its energy towards producing fruit rather than producing more foliage. Pruning your tomato plants at the suckers and removing yellowed leaves encourages healthy fruit production and prevents plant diseases. Unpruned foliage will eventually grow into new branches that will form fruit, but most experienced growers advise that tomatoes should be pruned to not only produce larger fruit earlier in the season, but also to protect the plants against pests and disease problems.
If you have fungal issues in your garden, airflow definitely should be considered, and you may want to prune your tomato plants to open up the foliage so air can easily circulate around the plant and its fruits. However, if your plants are not regularly bothered by leaf spots or other fungal issues, this probably isn't an issue of concern for you.
Additionally, if your tomato plants are lying on the ground, you might want to prune them, as contact with the soil encourages the development of fungal diseases. When leaves are forced into permanent shade, such as when the bushy plants are on the ground, the amount of sugar they produce is reduced. Instead of pruning, you can also stake your tomato plant to keep the leaves off the ground.
If you are growing tomatoes in containers, then pruning can be a good way to control the size of the plant, as otherwise it's easy for a vigorous tomato vine to outgrow its pot. Ideally, you should only choose compact tomato varieties for planting in containers.
When a tomato plant is pruned properly, all of the foliage receives adequate sunlight, and the plant is able to photosynthesize more efficiently, boosting growth and fruit production.
Before Getting Started
Not all types of tomatoes need to be pruned. If you are growing determinate tomatoes, you don't want to prune. Determinate tomatoes, often called bush tomatoes, are those varieties that grow to a fixed mature size, usually around four to five feet, although there are much smaller varieties as well. These tomatoes typically ripen all of their fruit within a few weeks. After fruiting, determinate tomatoes lose vitality and do not set further fruit. Therefore, pruning away suckers doesn't provide much benefit.
By contrast, indeterminate tomatoes do not have a fixed mature size, but continue to grow throughout the season, eventually becoming very large vines. Some varieties can reach as much as 20 feet in length, although most remain between 6 and 8 feet. Many of the most popular tomato varieties, including cherry tomatoes, heirloom tomatoes, and cultivars such as 'Big Boy,' 'Beefsteak,' and 'Brandywine' are indeterminate.
If you're growing indeterminate tomatoes, which produce fruit regularly over the course of a season, pruning is essential. This helps keep the commonly huge vines in control, and it encourages the plant to produce several large tomatoes instead of lots of foliage and many smaller tomatoes. To fit more plants into a small space, you'll want to prune your indeterminate tomato plants regularly and keep them staked or caged. This will prevent your plants from getting too large and bushy. However, indeterminate plants will still keep growing taller, and you'll keep getting fruit as long as the plant is growing.
Pruning Tomato Plants
If your goal is the healthiest tomato plants with the most bountiful harvest, then pruning your tomato plants is well worth the short time you'll spend on the task. While there are a few other methods of pruning, including pruning the plant's roots or pinching out the tomato plant's growing tips, the most common method is to prune away the suckers. Removing these unnecessary side shoots forces your tomato plant to focus more energy on fruit production, rather than foliage growth.
Click Play to Learn How to Prune Out Tomato Suckers
What You'll Need
Equipment / Tools
- Small pruning shears
- Stakes and twine (as needed)
- Household disinfectant
Locate the Suckers
Look for the tomato suckers, which grow in the "V" space between the main stem and the branches on your tomato plant. If left unpruned, 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.
Remove the Suckers
Suckers under 2 inches long can simply be pinched off with your fingers, but with larger suckers, use a pair of clean pruners, disinfecting them as you move from plant to plant to protect against spreading diseases.
Clip carefully to avoid tearing or nicking the tomato vine or nearby leaves. Make sure the cut is clean, without ragged edges or splits in the vine.
Whenever possible, remove the suckers when they are small. Removing large amounts of foliage at one time can stress the plant.
Remove or Stake Long Branches
Branches that are low-hanging and touching the ground should either be staked up or removed. Leaves touching the ground can be susceptible to bacteria, fungi, and viral infections that can spread through the rest of the plant.
Tomato cages make it easy to stake your plants and keep them upright. Choose a cage that's large enough to support the majority of your plant's length.
Common Tomato Pruning Mistakes to Avoid
While pruning tomato plants isn't complicated, doing it correctly helps promote vigorous growth and more fruit production. Here are some mistakes to watch out for.
Pruning Wet Plants
If your tomatoes are wet from rain or sprinklers, wait until the foliage is dry before pruning them. Clipping, pruning, or deadheading wet plants, fruit, or flowers can encourage the spread of harmful bacteria or fungi that might hurt or even kill your tomato plants.
Removing Too Many Leaves
Never prune away so much foliage that you reduce the amount of leaves on the plant by more than one-third. While tomatoes do need plenty of sunlight to grow and set fruit, overly intense sun and heat can lead to scalded tomatoes. Ideally, your pruning should leave an even spread of leaves around the plant to lightly shade the growing fruit from the most intense rays of sunlight. This is especially important in areas with very hot, dry summers.
Pruning With Dirty Tools
It's easy to spread bacteria and fungi from plant to plant by neglecting to clean your pruning shears between them. After you finish pruning each plant, wipe your pruning scissors or shears with 70% isopropyl alcohol before starting on the next plant. This is a good practice throughout your garden whenever you prune or clip any type of plant.
Not Removing Lower Leaves
While you'll focus on removing suckers to promote fruit production, don't neglect to remove the old, lowest leaves on your tomato plants as well. Fungal diseases usually strike the lowest leaves first, as often the fungus is spread from soil to plant. Removing older leaves often will remove fungal spores before they begin to grow. Also remove any yellowing or unhealthy leaves from any location on the plant each time you prune.
Letting Suckers Grow Before Pruning
Waiting too long before pruning away suckers means your tomato plants wasted energy in unnecessary foliage growth that could better have been spent on growing fruit. Plus, suckers can become heavy and weigh the plant down while reducing airflow around the foliage. If you've waited too long, and the suckers are now large and established offshoots, it's best to only prune the sucker partially to avoid shocking the plant. Called Missouri pruning, this involves pruning the suckers down to right above the second set of leaves.
Pruning Tomato Plants. University of New Hampshire Extension