Pruning tomato plants is a hot topic among home gardeners this time of year. To prune, not to prune? I’m firmly in the “not to prune” camp.
I often hear gardeners say they remove leaves or pinch off “suckers” (side branches) so their tomato plants can “put energy into making flowers and fruits.” To my botanist brain that makes zero sense. Here’s why: leaves are the plant’s “engine.” Leaves are where photosynthesis happens, the process plants use to make energy from sunlight, carbon dioxide and water. The energy from photosynthesis powers plants to grow, flower, and for the flowers to become fruits.
Pruning removes leaves. That means, pruning LIMITS the plant’s ability to make the energy it needs to grow, flower, and fruit.
Pruning => fewer leaves => fewer flowers => fewer fruits.
A while back, I asked two experts about pruning tomatoes: Renee Shepherd, founder of Renee’s Garden seed company, and professional tomato breeder Doug Heath.
Shepherd’s team experimented with pruning tomatoes at their test gardens across the country. They found that pruning did not increase production, but it did result in sun scalded tomatoes. The only time they prune a tomato plant, she said, is if it outgrows its space.
Breeder Doug Heath agreed that pruning tomato plants doesn’t make sense, except in an effort to tame indeterminate tomato vines that grow into a tangled mass of branches and greenery. He finds that fruits grow a little larger when he tips the plants back, but if you don’t mind a huge plant and slightly smaller fruits – and you have the space – there’s no reason to prune. Nor should you prune determinate (bush-type) tomato plants. In fact, Heath cautions, if you prune, you risk spreading tomato viruses and other diseases via your pruning shears.
Are there times to prune? Yes, but just a few:
- Prune off lower leaves at planting. Planting tomato seedlings is the rare instance when we bury most of the stem. Have you ever noticed tiny bumps on the stem of tomato plants? Those bumps are latent roots that sprout when buried. The additional stems make for strong tomato plants. While the stems are good to bury, the leaves are not, so pinch off the lower leaves rather than bury them.
- Prune off leaves that touch the soil. These leaves are a highway for molds, fungi, and other maladies that come from soil. Remove the lower leaves to protect the plant. Make sure there are no branches touching the soil either.
- Remove one or two whole branches from the center of any overly dense tomato plant. Tomato plants are very vigorous growers – especially indeterminate varieties – cherry tomatoes and others – that grow as long vines. Sometimes, all those branches and foliage prevent good airflow and sunlight from reaching the center of the plant. Fruits don’t ripen well, and leaves can develop powdery mildew. Removing a few of the central branches, not just leaves, helps avoid these problems.
Giving up on pruning tomatoes saves a lot of time, and results in bigger, stronger, more productive tomato plants. That’s what we all want!
