Tomatoes have been such popular plants for generations that a wealth of lore has developed around them. The age-old battles, like caging versus staking, planting horizontally or vertically and small-fruited varieties versus beefsteak types, replay year after year. Few tomato issues stir up the same controversy as as pruning.
Tomato plants grow from a set point at the end of the vine called the growing tip. This vegetative section enlarges, sending out side branches with fruiting clusters as the plant develops. Indeterminate tomatoes may have several growing tips, all trying to create new branches and flowering clusters simultaneously that will end up competing with one another for limited resources. Determinate tomatoes don't have this problem because every growing tip terminates at a set point with a fruit cluster, instead of developing one off to the side, naturally limiting their own growth.
Containing Tomato Growth
Trimming side shoots and branches on indeterminate tomatoes is the best way to contain their growth, but not because the plant is stunted -- as long as the growing tips are intact, the vine will continue to lengthen and send out side shoots and suckers. Tomatoes, like other vines, benefit from training to a support and the best way to do this is to remove extra branches and pinch out suckers. Once one or two main trunks are established, you should remove additional suckers and branches as they develop because they rob flower clusters of the nutrition they need to produce fruit.
Staking and caging have long been used to keep tomatoes from sprawling on the ground, preventing fruit damage and keeping the plants more easily contained. As it turns out, pruning and training tomatoes to a vertical form also helps prevent disease, often induces earlier fruiting and causes a thicker canopy of leaves to develop to shade fruits. A 2000 Iowa State University research team showed that pruned plants generally produce larger, more uniform tomatoes.
There are two main methods of removing tomato branches: simple pruning and Missouri pruning. Simple pruning involves snapping off young, tender growth while it is small, creating a tiny wound that heals quickly. This way, the plant wastes no energy trying to grow that sucker or branch. Missouri pruning is often reserved for situations where the side shoots have gotten out of hand, becoming large and hard. Simply removing these at the branch crotch may cause severe wounding and shock the plant, but pinching off the growing tip below the cluster of end leaves is much less traumatic.
- University of Maine: Pruning Tomatoes
- Iowa State University Extension: Tomato Cultivar Trial and Pruning Observation
- University of California Statewide Integrated Pest Management Program: Pruning Your Tomatoes
- University of California Department of Agriculture and Natural Resources: Growing Tomatoes in the Home Garden
- University of California Davis Good Life Garden: Tomatoes: Techniques for Staking and Pruning Your Tomato Plants
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