While tomatoes may appear delicate, they’re actually quite robust. If your tomato plant is growing out of control, you may be asking yourself how to prune indeterminate tomatoes.
These plants are so resilient that pruning indeterminate tomatoes is just a matter of when and how much to snip. If you’re ready to tidy up your garden and produce some plump tomatoes, you’re in the right place.
What are Indeterminate Tomato Plants?
Determinate and indeterminate tomatoes may appear the same at first, aside from the labeling on their seed pack or transplant container, but their height is an easy distinguisher.
Indeterminate tomato plants have no genetic limit on how tall or wide they can grow. They will often reach 10 to 12 feet vertically with consistent watering and fertilizer, and their growth is only (naturally) limited by the length of their growing season.
These vining tomato plants trellis well, and produce tomatoes for a longer span of time than determinate tomatoes. When growing multiple indeterminate tomatoes, they must be pruned to a single stem in order to maximize space (at least a foot between plants) and discourage infinite growth.
Examples of indeterminate tomato varieties include Early Girl, Better Boy, and Fantastic. Each of these can grow well in a large container or a garden space that is at least four feet in diameter. Aside from longer growth periods and more impressive foliage, indeterminate tomatoes also tend to produce more flavorful fruit.
Determinate tomatoes are genetically programmed to only reach a certain height, usually five feet tall or less, and to produce only a certain amount of foliage and flowers. These bush tomatoes follow a pattern in which their fruit ripens all at once before the plant dies.
These tomatoes require significantly less pruning, and so are desirable for gardeners who prefer low-maintenance field or container gardens. Bella Rosa and Mountain Spring are two popular determinate tomato varieties.
How to Prune Indeterminate Tomatoes
1. Prepare Your Tools
Before pruning indeterminate tomatoes, you’ll want to ensure that you have access to garden gloves (or freshly washed hands) and a pair of sharp garden clippers. The best pruners to use for tomato plants are bypass pruners, which are adept at navigating tight spaces between branches, and are suitable for pruning live stems. Always disinfect your pruners before use.
2. Understand the Basic Anatomy of the Tomato Plant
Before pruning indeterminate tomatoes, understand the basic anatomy of the plant:
Crown – This is the top region of the plant where flowering begins. This is where you’ll choose a strong sucker to be responsible for the height and photosynthesis of the plant.
Main Stem – The center stalk of the plant can be called the “main stem” or the “leader.” This is a tomato sucker that you select as the most viable stem for your tomato growing needs. All other suckers are removed, but leave the top of the main stem uncut. This is the main growing point.
Axil – This is any location on the plant where a branch connects to the main stem.
Sucker – This is a new branch that grows between the main stem and an axil. Suckers will become stems unless you prune them. When they are small, they look like a tiny leaf.
Leaf – A site of photosynthesis, tomato plants feature compound leaves that are composed of leaflets.
Flower Cluster – These are areas where a series of smaller branches culminate in several flowers. Don’t remove these after the middle of the growing season.
Fruiting Cluster – When a flower cluster is pollinated, these groups of yellow flowers begin to develop into fruits. These should also be left intact after the midpoint of the growing season.
Knowing these areas allows you to identify growing sections (suckers) that require pruning.
3. Understand Why Pruning Indeterminate Tomato Plants is Important
The suckers of indeterminate tomato plants will continue to grow indefinitely if they aren’t stopped. This results in the plant expending energy on expansion rather than producing the juiciest fruits. Pruning encourages larger fruits that arrive earlier and in greater quantity than they would otherwise.
Since suckers become stems when they grow, they will attempt to produce fruit if left to their own devices. While extra tomato branches may sound nice, it’s important to remember that low-hanging fruit will weigh down branches and rot on the ground. Also, the more places your plant is trying to produce tomatoes from, the less bountiful and tasty they will be.
Clearing away all suckers between the ground and the second flower cluster will maximize the airflow and light penetration of your plant. This optimizes plant health by keeping dense foliage near the bottom while the canopy deters insects and disease. Suckers hanging out near flower and fruit clusters will suck up their nutrients like vampires, leaving only emaciated tomatoes.
Prevent disappointing tomato yields by removing all suckers around clusters. When you’re done pruning, you can plant the suckers to develop new tomatoes!
Pruning indeterminate tomatoes also allows for closer plant spacing. When trellising tomatoes, you can prune just above the trellis to help prevent the tomato from entangling itself or becoming diseased as a result of drooping after reaching its maximum vertical height.
4. Choose Your Tomato Pruning Method
There are two primary methods of pruning indeterminate tomatoes:
Simple pruning – Remove the suckers from the main stem entirely by pinching them and plucking them away. Bend the sucker between your fingers until it snaps, or use your pruners to sever thick stems.
Missouri pruning – Only pinch the leaflets at the end of each sucker, and allow the two base leaflets to remain as shade and nutrient providers. This is best suited for warmer zones where the risk of sun scald is higher. It does increase the frequency of pruning required, and is best used for large suckers. This prevents disease from reaching the main stem and shocks the plant less.
5. Know the Rules of How to Prune Indeterminate Tomatoes
Some key rules to pruning indeterminate tomato plants include:
- Never work with a wet tomato plant. Water droplets can transfer fungus and bacteria from the soil (or your hands) that infect your plant.
- Remove everything that touches the ground. Your plant can be exposed to diseases in the soil by this route as well.
- Prune all dead, diseased, broken, and dying branches immediately. These are other entry points of disease, the spread of which is best stopped by cutting off the infected portions.
- To remove suckers, pinch the sucker at the base and gently bend it back and forth until it snaps off. This is best for small suckers. Suckers that have already developed hardy stems will require a clean cut, a little bit away from the main stem, using your bypass pruners.
- Removing suckers while they are small helps to prevent accidentally stripping the outer layer of the main stem, which would leave the plant vulnerable to fungus and pests.
- Leave enough foliage on your plants to protect developing fruit clusters from sun scald, a sunlight-induced burn.
Pruning indeterminate tomatoes begins by removing any lower leaves that may come into contact with the dirt as you’re planting it. You need to be able to plant it sufficiently deeply. You can also remove flowers to encourage more foliage to grow. Resist pruning any further for at least four weeks so that the young plant can recover from the shock and develop new growth.
Mulching your tomato plant will prevent diseases from splashing onto the plant whenever rain (or your own watering) comes into contact with the soil. It also maintains soil temperature and moisture levels, allowing for less frequent watering and fewer weeds.
If your plant is not yet 12 to 18 inches tall, it’s important to remove all flower clusters. This tells your plant to send more energy down to the roots. Once the plant reaches an adequate height, allow the next flower cluster to develop. Snip off suckers that develop below these clusters, but allow some leaves to remain on the stem to provide shade and nutrients.
When pruning indeterminate tomatoes late in the season, remove a small handful of leaves each week from below the fruit clusters. This promotes early tomato development. Just remember never to remove more than a third of the entire plant throughout its growing season, or else it may experience sun scald.
If you already see lots of fruit developing and new flowers are still blooming, you can trim flower clusters in order to limit the number of tomatoes, maximizing their size and flavor. The fruit formed by suckers arriving in the late season will always produce low-quality fruit and should be pruned.
You can also try root pruning indeterminate tomatoes. This involves using a spade to make a cut a few inches out from the main stem and nearly a foot into the ground, followed by cutting halfway around the plant. This tells the plant to speed up the maturation of ripe tomatoes and can be utilized when tomato fruit are first appearing.
At four weeks before the first frost in your region, remove the top of the main stem. This action, called “topping,” instructs the plant to send all of its remaining sugars and nutrients to the ripening fruit. This helps the fruits ripen faster, which is especially important in colder areas with short seasons.
If you enjoy green tomatoes, then you can allow the plant to continue growing, un-topped, until the season ends and it dies.
Wrapping Up Pruning Indeterminate Tomatoes
Pruning indeterminate tomatoes is all about removing suckers and weak spots with patience and consistency. Once you get the hang of how to prune indeterminate tomatoes, it can be a meditative garden experience that yields delicious fruits. Keep reading about the difference between determinate and indeterminate tomatoes to decide which variety is best for your garden.