As a plant grows, it develops side shoots, called suckers. These side shoots form on the “V” between the main stem and a set of leaves. If you leave these suckers on the plant they will grow exactly like the main stem producing leaves, flowers and fruit.
Without pruning, your plants will have more main stems so will grow more fruit. However, that fruit will be smaller and take longer to mature because the plant will be concentrating it’s energy on growing more stems and more foliage.
On the other hand a properly pruned tomato plant will use all those plant sugars to grow healthier, stronger and bigger fruit with more concentrated flavor. We believe in quality over quantity, so we choose to prune those side shoots. This way we might get less tomatoes, but they will be bigger, more flavorful and will ripen earlier.
Single stem pruning:
When you prune you can choose to go with one main stem (cutting off all the suckers that grow off the main stem), or you can allow some of those suckers to grow – for up to four main stems. There is no right and wrong way to prune, but when you are deciding how many stems you want to allow on your plant, keep in mind that tomatoes like good air flow and do not like to stay wet. Keeping your tomato plants dry means that bacteria and fungus have less of a chance to thrive and multiply.
In the heat and humidity of North Carolina, we like to keep it to just one single stem. In addition to keeping the plant drier with better air flow, a single stem allows all the leaves to get lots of sunlight. Since there isn’t as much competition from too many stems and foliage, all the sugars that are produced are directed straight to the fruit.
How to prune your tomato plants
Any sucker that is not destined to become a stem should be removed. I like to leave one main stem, so I remove all the suckers off the plant.
It’s always best if you remove the side shoots when they are still young and tender. Simply grab the sucker near the base with your thumb and index finger and gently bend it back and forth. The sucker will easily snap off and should heal over quickly.
TIP: Toss these shoots in your compost heap, or place them in a jar of water to keep them from drying out. When you are done pruning, root the suckers in soil and they will grow into an identical clone of the original plant.
Side shoots begin growing from the bottom of the plant up. The lower the shoots, the stronger they will be because they have access to a higher concentration of sugars. Regardless of how many stems you choose to leave on your plants, all suckers below the first flower cluster should always be removed otherwise they will compromise the strength of the main stem.
Other than snapping off all suckers below the first flower cluster, only indeterminate plants should be pruned. Determinate plants have a predetermined number of stems, foliage and fruit. By further pruning determinate plants you will only be diminishing your harvest.