How To Prune Tomatoes

Pruning offers many benefits to your tomato plants. It helps to increase air circulation, which lessens the risk of disease and pest infestation. While pruning tends to lessen the size of your yield, larger, more delicious fruit are produced as a result. Pruning allows more sunlight to reach the leaves, increasing the amount of sugar that is produced. Pruning also allows the tomato plants to focus all of the nutrients obtained from water, soil and sun into the few leaves and fruit they are producing. Here are some tips on how to prune tomatoes properly.

Indeterminate tomatoes are the vining variety and these are the ones you most need to prune. Determinate, or bush varieties, generally do not benefit. Bush tomatoes produce all of their tomatoes at once and it is somewhat counter productive to prune. The exception for bush tomatoes is pruning off unhealthy leaves and stems, allowing a little more room for good light and aeration and pruning suckers on the lower part of the plant only.

If left to their own devices, tomato plants will grow rapidly and awkwardly, eventually toppling over and growing several main stems for only one plant. This will quickly become a tangled mess and a haven for pests and disease. For this reason, tomatoes need support and simple pruning to maximize their potential to produce delicious fruit.

Single stem vines that are properly pruned will allow full sun to reach each of the leaves, which maximizes photosynthesis resulting in the production of more sugar, which provides the delicious taste of each tomato. Tomatoes will grow larger and faster, producing fruit earlier under these conditions. Properly pruned tomato plants receive better air circulation and dry off faster greatly limiting the risk of disease as well. They are easier to care for and take up far less space in the garden.

Priority number one: you need to prune suckers. ‘Suckers’ is a name given to the secondary growth that springs up between the main stem and the leaf stems. They protrude from this axis at about a 45° angle, always above the leaf stem. If left to grow, they will develop into their own stems, producing their own leaves and fruit. While this can increase the amount of tomatoes that are produced, this comes at the expense of size and quality because they compete with the plant’s main stem leaves for nutrients.

Pinch suckers off before they get too large. Don’t cut them off, just pinch them between your fingers and bend them a bit until they pop off. This is called ‘simple pruning’ and should not take much effort leaving only a small wound that heals quickly. Cutting increases the risk of infection. If suckers are left to grow too big, they will be too firm and difficult to pinch off. In this case, you can cut or clip them but only clip the tips, just above their first set of leaves. This is called ‘Missouri pruning’ and will keep any infection far away from the main stem and will not cause any harm to the plant. These two leaves will also provide shading that can be helpful to fruit.

Note: Prune all suckers that appear between the soil and the first set of flowering leaves on determinate varieties of tomatoes as well. This will provide a good amount of space between the soil and the foliage, lowering the risk of pests and disease.

Prune off dead, dying or diseased leaves and stems. This will keep them from spreading to the rest of the plant.

Prune any leaves that come in contact with the soil. Soil is a place where many pests and disease live and this will help keep them at a safe distance.

Top off your plants when there are only about 30 days left until the first frost of the fall. Slice off the top stem, below any leaves not producing fruit, so they don’t produce any more leaves and focus their energy in what they have already started. Remove all growing tips on the main leaf vines as well. This may be difficult to do, but it will ensure that all fruit ripens before the end of the growing season.

The recommended number of main stems is 6-8 for every variety of tomato except cherry tomatoes, which do well with 12-14 main stems.

Tie tomato vines to stakes properly, both to train them to grow steadily upwards as well as to support the weight of the fruit as it develops. See our article on how to stake tomatoes for more information.

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