Ask Gardenerd: Pruning Tomatoes

Summer is the perfect time for this question from Jeff Bremer: “Hi Christy, What’s your opinion on pinching-off the “branches” that sprout out of tomato plants? Some of my friends don’t pinch at all, but my neighbor pinches his plants back so he has only one “stem.” Thx, Jeff “

Ah yes, to pinch or not to pinch, that is the question. What are we pinching? Side shoots and suckers. Side shoots are additional vines that grow from the base of the center stem. Suckers are potential vines that grow from the junction of the main stem and a leafy branch. Tomato lovers will argue all day about this one, but it comes down to two things: taste and space.

Tomato sucker growing from junction of main stem and leaf.

Tomato sucker growing from junction of main stem and leaf.

Space

If you have space, you can let your tomatoes side-shoot all you want. Most people don’t have a lot of space, so pruning becomes important in maintaining control in a small garden. For those who use stakes instead of cages, pruning is critical to maintain one main stem. Side shoots end up on the ground, which makes the plant vulnerable to diseases.

Short cages are another reason to prune. Tip pruning prevents tomatoes from vining over the tops of your cages. Tip pruning also causes a chemical response from the plant, allowing side shoots to becomes “leaders,” which could be a good thing. You end up with more vigorous growth to fill up the cages, and possibly more fruit.

Kellogg's Breakfast Tomato

Kellogg’s Breakfast Tomato

Taste

Suckers are so named because they suck the energy away from producing fruit. “Energy” can mean sugars and sweetness, or nutrients and vigorous growth. The general rule of thumb is to start pruning suckers once you have 4 trusses (or sets) of fruit on the vine. The rules can be bent if you have incredibly rich soil. Tomatoes are heavy feeders so they need a constant supply of nutrients to keep producing. Suckers draw focus away from ripening fruit, so remove them if you have to feed your soil often.

Personally, I prune suckers only if the plant is vigorous. Since I’m growing some flimsy heirlooms, that isn’t always necessary. I also use the Tomato Crib (instructions for how to make one can be found in Gardening for Geeks) so I let the tomatoes that I grow in those cages sprawl. I also use Tomato Ladders from Gardeners Supply, and in those cases, I train my tomatoes to one vine to avoid chaos.

See our blog post on suckering here. Read our guest blog post on pruning tomato specifics here.

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2 Responses to Ask Gardenerd: Pruning Tomatoes

  1. Jeff Bremer says:

    Hi Christy,

    Thanks for answering my question. I’m curious about something you wrote as it seems counter-intuitive.

    If suckers take energy away from a plant, why would you pinch them only if a plant is vigorous? Why wouldn’t your flimsy heirlooms benefit from pinching, if pinching leaves more energy for the rest of the plant?

    Thx, Jeff

    • Christy says:

      HI Jeff, Sorry that sounds conflicting. I am accustomed to heirlooms being less vigorous in general, meaning fewer leaves and stems, which means less of a need to prune. If you live in an area where sunscald is not an issue, prune away. Otherwise leave some canopy of leaves to protect those awesome heirlooms.

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