Tomatoes: To Prune or Not to Prune is a Very Good Question

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Tomatoes are one of the most popular plants to grow in a vegetable garden. Whether you've got a tiny patio or as much garden space as you want in the country, you can grow tomatoes. They're reasonably easy to take care of, they produce a fantastic amount of fruit per plant, and homegrown tomatoes are so much tastier than store-bought tomatoes. 

While tomatoes are fairly simple to grow, there are a few little quirks about them. Pruning is one of those tricky tomato topics that can be hard to make sense of as a beginner. Many people say you must prune your tomatoes or your plant will be a failure; others say they never prune and get loads of fruit. 

It's not quite as simple as pruning or not pruning your tomatoes. There are reasons why one may need to prune and some may not.  Tomatoes are a vine that form new side branches as they grow. Usually referred to as suckers these new shoots can be removed (or de-suckered) for reasons such as, increasing air flow to prevent fungal and bacterial diseases, concentrating the plant's energy into growing fruit rather than more branches, and/or keeping leaves off of the ground where they could pick up pathogens.

There are types of tomatoes that need to be pruned and types that don’t. When you're choosing your tomatoes, whether you're buying seeds or transplants, it's good to know exactly what kind you're getting, so you know what kind of support and space they will need and whether or not you should prune them.

Tomatoes to Prune

Pruning indeterminate tomatoes will benefit them immensely. What are indeterminate tomatoes? 

Indeterminate tomatoes are plants that keep growing all season long and should be pruned. They keep getting taller and taller, producing fruit as they go. Most heirloom and cherry tomato plants are indeterminate and require pruning. These plants do best if they have a tall vertical structure to climb. People often grow these tomatoes in greenhouses, where they have a structure to hang ropes from, but they can also be grown in large cages.

Pruning determinate tomatoes may actually decrease your potential harvest because you may remove limbs that would have produced flowers and eventually fruit. ​

To prune a tomato, you'll look for suckers, new leaf sprouts poking out from the point where an existing branch meets the central stem. These snap out pretty easily when they're still small, but you may need scissors or pruners if they get bigger. Somehow one or two always seem to hide and grow very large before they are caught. It will not damage the plant to take them out, even if they're quite big. 

As your indeterminate tomato gets taller, you can also remove the lower leaves below the fruits. This type of pruning helps improve air circulation and prevent diseases, but leaves that are above fruits will help shade the tomatoes from the sun and should be left to prevent sunscald.

Tomatoes Not to Prune

Determinate tomatoes will grow to their mature size, then stop. These types of tomatoes do not require pruning to thrive. Once they reach full size, they'll start all their fruit around the same time. Because of this determinate tomatoes should only be pruned along the base of the stem to remove suckers from the bottom up until the first cluster of flowers, at this point it will already be putting its energy into fruit production and further pruning is not necessary.

Determinate tomatoes still need good support, but cages are usually a better solution than ropes. Because determinate varieties usually produce and ripen all of their fruit in a shorter time frame, the limbs can get very heavy and may break branches if the plant isn't supported well enough. 

How to Know What Kind of Tomato You Have?

The plant tag may or may not tell you if a tomato is determinate or indeterminate, or say that the tomato needs pruning, or doesn't. If it doesn't have this information or you’ve tossed out the tag, a quick internet search with the name of the tomato will tell you pretty quickly which type of plant your tomato is, and then you can better judge whether or not it needs pruning. 

Though there is no perfect recipe for how much to prune, if you are paying attention to the overall goals for pruning, creating a balance between leaf and fruit growth, encouraging air flow, and removing diseased leaves, then you are probably going to have good results.