A salt bath for your tomatoes?

This morning I got an email from one of my gardening colleagues, wondering about the wisdom of watering tomato plants with salt water.  He had a link to a UC Davis website which tacitly endorses spraying tomato plants with 10% salt water “to increase their nutritional value and taste.” Unreferenced “worldwide studies” are mentioned, along with the “major potential benefit of providing irrigation for crops in areas with freshwater restrictions.”

Before we deal with the impracticalities and out-and-out harm of using salt water for irrigation, let’s look at why this practice would work on tomatoes.  By training I’m a plant stress physiologist (and I’m well versed in the primary literature on this topic).  Watering tomato plants with a salt solution imposes a drought stress on the entire plant, as less water is taken up under these conditions.  So leaves and fruits are smaller and they may produce stress-induced biochemical compounds in response.  The upshot is that you have smaller tomatoes with a higher concentration of various solutes, some of which might be tastier or more beneficial to humans.

Guess what?  You can do the same thing by decreasing irrigation during fruit set!  Less water means smaller fruit and increased concentrations of sugars and other plant compounds, and voila!  So you can skip that step of adding salt water and just cut back on irrigation to induce a mild drought stress.

So…why in the world would you dump salt water on your garden soil?  The article blithely dismisses this:  “Many are still concerned about salt causing soil degradation and rendering some seawater-treated tomatoes inedible, but scientists cite that plants thrive in balanced soil containing both macro- and micronutrients.”  Sorry, but sodium is NOT a micronutrient for most plants and does NOT contribute to a “balanced soil” in one’s vegetable garden.

An ironic twist to this whole article is that most of the research that’s been done is relevant to arid parts of the world (the Middle East, primarily) where saline soil conditions and limited water are common.  I can’t imagine what they would think about people who would deliberately contaminate good soil by adding salt water to it.

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Linda Chalker-Scott

Dr. Linda Chalker-Scott has a Ph.D. in Horticulture from Oregon State University and is an ISA certified arborist and an ASCA consulting arborist. She is WSU’s Extension Urban Horticulturist and an Associate Professor in the Department of Horticulture, and holds two affiliate associate professor positions at University of Washington. She conducts research in applied plant and soil sciences, publishing the results in scientific articles and university Extension fact sheets. Linda also is the award-winning author of five books: the horticultural myth-busting The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010) from the University of Washington Press and Sustainable Landscapes and Gardens: Good Science – Practical Application (2009) from GFG Publishing, Inc., and How Plants Work: The Science Behind the Amazing Things Plants Do from Timber Press (2015). Her latest effort is an update of Art Kruckeberg’s Gardening with Native Plants of the Pacific Northwest from UW Press (2019). In 2018 Linda was featured in a video series – The Science of Gardening – produced by The Great Courses. She also is one of the Garden Professors – a group of academic colleagues who educate and entertain through their blog and Facebook pages. Linda’s contribution to gardeners was recognized in 2017 by the Association for Garden Communicators as the first recipient of their Cynthia Westcott Scientific Writing Award. "The Garden Professors" Facebook page - www.facebook.com/TheGardenProfessors "The Garden Professors" Facebook group - www.facebook.com/groups/GardenProfessors Books: http://www.sustainablelandscapesandgardens.com

12 thoughts on “A salt bath for your tomatoes?”

  1. Linda, keep in mind that this particular blog & garden are NOT part of UCD’s ag research program, which is stellar. Rather, this garden is part of the Robert Mondavi Center For Wine & Food Science (not soil/ag/garden science) on the UCD campus. It is intended for ornamental & educational (very basic, from what I’ve seen) purposes, but not to promote and disseminate research.

  2. Laura, I’ll grant you that…but most people would look at this as a .edu site and think, “okay, they’re a university, so the information must be good.” And if this site is intended to be “educational,” then it needs to be accurate.ckquote>March 16, 2011
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    Paul W@ Laura B. Seriously?! Wrong info is wrong info. The stellar part of UCD, should smack down the Mondavi misinformation quickly. PARTICULARLY since UCD has a bit of a tomato research reputation to uphold. March 16, 2011
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    Rebecca MActually, there was a Rutgers study on watering your tomatoes with salt water (or using a sodium nitrate fertilizer) a couple years ago. There was a short article about it in the American Vegetable Grower and Growing for Market last year.

    http://www.njfarmfresh.rutgers.edu/documents/TomatoSalt2009.pdf

    http://njaes.rutgers.edu/pubs/plantandpestadvisory/2010/vc031710.pdf March 16, 2011
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    MattBizarre… UCD needs to clue in to this blog using it’s name.March 16, 2011
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    KandiSigh … UCD is usually so reliable, especially with agriculture. This post is so odd. March 16, 2011
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    Linda Chalker-ScottRebecca, I looked at these online sources, but unfortunately the authors have not published their data in the scientific literature. So at this point their information is only anecdotal – it’s impossible to assess their resultsMarch 17, 2011
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    Jan A friend gave a teaching “moment” at a gardening meeting recently saying adding sugar to the watering can makes tomatoes sweeter. That didn’t sound too logical to me. Have you come across this before? I know some people add molasses to their compost piles. Buying ingredients for the compost kind of defeats the whole recycle, reuse, etc. part of composting for me.March 17, 2011
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    DebWe experienced the benefits of drought on tomatoes last summer, when Massachusetts baked under dry summer skies for months. We did our best to water the garden from the rainbarrel, but when that ran out had to use gallon jugs. Lugging them back and forth from the far-away spigot kept watering to a minimum. We got lots of tomatoes, actually, for the stress we put the plants through, and though the fruits were pretty uniformly smaller than usual, they were really, really flavorful. Salt is cheap, but no water is even cheaper, and doesn’t degrade the soil.March 21, 2011
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    alan haighI was raised in the west up a coastal canyon above Malibu. I became a serious gardener in my teens and was surprised how much sweeter the neglected volunteer tomatoes growing on the beach sand a bit above the tide were compared to my coddled plants up the canyon.

    I always figured it was the salt, but in retrospect it may have been drought stress or some combination of the two. I remember reading in some popular type literature of adding a TBS of salt to water for sweeter tomatoes. This was 40 years ago.

    I don’t see how a little salt on the foliage wouldn’t be a worthwhile path to more flavorful tomatoes if it’s affective but in the west I certainly wouldn’t want to contribute to more sodic soil.May 26, 2012
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    Jack PearsallI was doing some research concerning growing tomatoes and I came across your discussion. I publish a blog, http://www,tomato411.com
    I actually did an experiment with “soft water” watering for the tomatoes and just plain well water for the other control group. Oddly enough, I found there was very little difference if any between the two sets. I’ve been tempted to try it again with some different varieties, I guess I’ll have to get serious about science…..☺…Thanks

  3. @ Laura B. Seriously?! Wrong info is wrong info. The stellar part of UCD, should smack down the Mondavi misinformation quickly. PARTICULARLY since UCD has a bit of a tomato research reputation to uphold.

  4. Rebecca, I looked at these online sources, but unfortunately the authors have not published their data in the scientific literature. So at this point their information is only anecdotal – it’s impossible to assess their results

  5. A friend gave a teaching “moment” at a gardening meeting recently saying adding sugar to the watering can makes tomatoes sweeter. That didn’t sound too logical to me. Have you come across this before? I know some people add molasses to their compost piles. Buying ingredients for the compost kind of defeats the whole recycle, reuse, etc. part of composting for me.

  6. We experienced the benefits of drought on tomatoes last summer, when Massachusetts baked under dry summer skies for months. We did our best to water the garden from the rainbarrel, but when that ran out had to use gallon jugs. Lugging them back and forth from the far-away spigot kept watering to a minimum. We got lots of tomatoes, actually, for the stress we put the plants through, and though the fruits were pretty uniformly smaller than usual, they were really, really flavorful. Salt is cheap, but no water is even cheaper, and doesn’t degrade the soil.

  7. I was raised in the west up a coastal canyon above Malibu. I became a serious gardener in my teens and was surprised how much sweeter the neglected volunteer tomatoes growing on the beach sand a bit above the tide were compared to my coddled plants up the canyon.

    I always figured it was the salt, but in retrospect it may have been drought stress or some combination of the two. I remember reading in some popular type literature of adding a TBS of salt to water for sweeter tomatoes. This was 40 years ago.

    I don’t see how a little salt on the foliage wouldn’t be a worthwhile path to more flavorful tomatoes if it’s affective but in the west I certainly wouldn’t want to contribute to more sodic soil.

  8. I was doing some research concerning growing tomatoes and I came across your discussion. I publish a blog, http://www,tomato411.com
    I actually did an experiment with “soft water” watering for the tomatoes and just plain well water for the other control group. Oddly enough, I found there was very little difference if any between the two sets. I’ve been tempted to try it again with some different varieties, I guess I’ll have to get serious about science…..☺…Thanks

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