Pruning tomatoes and tomato suckers

Most of us have our tomato plants in the ground by now and are anxiously awaiting that very first ripe tomato. Before we reach that point, however, there are a few issues which need to be addressed. One of these is pruning; that is, shaping the plant so that it will grow and produce the maximum number of fruit and of the size which we desire.

Tomatoes are generally classified as either determinate or indeterminate. Determinate tomato plants have a genetically predetermined number of stems, leaves and flowers (and thus fruit). Their growth follows a pattern of vigorous vegetative growth followed by a flush of flowers and fruit, after which there is a period of final leaf expansion and an end to further vegetative growth.

Commercial growers like this type of tomato because most of the fruit can be harvested at once. Examples of popular determinate varieties are Amelia, Roma, the BHNs, Better Bush, Celebrity, Talladega, Top Gun, Tasti-Lee and many others. These varieties grow shorter and produce less fruit than their indeterminate counterparts.

Indeterminate tomato plants continue to grow and produce leaves, stems and fruit as long as growing conditions are favorable. Indeterminates can have one main stem or several stems, depending on how they are pruned. The fewer the number of stems, the larger but fewer the fruits will be. Popular indeterminate varieties include Beefsteak, Beefmaster, Better Boy, Big Beef, Big Boy, Park’s Whopper, Goliath, among others.

Tomato pruning involves the issue of retaining or removing parts of the tomato plant known as suckers. Suckers are side shoots which appear in the axils, or crotches, between the leaf petioles and the main stem. If allowed to remain, suckers will grow just like the main stem, complete with flowers, fruit and more suckers.

Why are tomato suckers pruned? This is done because the suckers compete with the main stem and its fruit for nutrients. While it is true that more fruit will result from leaving the suckers to grow, the resulting fruit will be smaller and the plant will become more cumbersome and thus harder to support. Pruning, therefore, is much like trimming a shrub.

Pruning also affects the health of the tomato plant. The leaves of a pruned plant tend to dry faster, being exposed to the sun, so bacteria and fungi have less opportunity to spread and cause diseases. A more compact and well-trained plant, directed upward rather than outward, will tend to have fewer problems with leaf spots and fruit rots because its leaves stay drier and free of soil residue, which often harbors disease-causing organisms.

On the other hand, not pruning suckers will cause the tomato plant to develop more leaf cover and thus more shade for ripening fruit, which can minimize sunburn and scalding. This can be a distinct advantage for varieties that naturally form less leaf cover.

Is pruning necessary? Pruning suckers is not a requirement and many gardeners do not even bother with it at all. However, if you are one of those who do, you will appreciate knowing that whether to do so or not depends on the type of tomato you are growing.

Determinate tomatoes need no pruning other than the removal of all suckers below the first set of flowers. Additional pruning will not affect fruit size or plant vigor. If pruning is done anywhere above the first flower cluster, the tomato harvest will be reduced. Since indeterminate tomato plants can get extremely large and will keep producing tomatoes all season, they can handle some pruning. If you leave all the suckers to grow, your plants may become heavy and out of control if not well supported. On the other hand, removing all the suckers will result in a more compact and manageable plant, but it will also lessen your tomato yield.

As long as your tomatoes have strong main stems, it’s fine to leave a few suckers on the plant. The general recommendation is to leave two or three suckers to improve yield, but not to let every sucker grow.

Tomato pruning is more trial and error than precision, so look at it as an experiment. When you first start pruning, do less rather than more. If you grow the same varieties year after year, you’ll get a feel for how they respond to pruning.

Tim Lewis is a Georgia Green Industry Association Certified Plant Professional, gardening writer, former Perry High School horticulture instructor, and former horticulturist at Henderson Village and Houston Springs. He and his wife, Susan, own and operate Lewis Farms Nursery located on Hwy 26 two miles east of Elko, where he was born and raised. He can be reached at (478) 954-1507, timlewis1@windstream.net, and at LewisFarmsNursery.com.

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