Garden Myth: Is Dish Soap Safe for the Garden and the Science Behind It

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Ill.: clipartkey.com & clipartstation.com

Guest article by Jeffrey Douglas

With more and more people “greening” up their daily living, it isn’t surprising to see this trend move into the garden. With so many different chemicals out on the market and rising recognition of the harmful effects of commercial pesticides, it’s no wonder people want to find a more natural solution. Look at it this way, do you really want to put more chemicals into your body that our commonly purchased foods already contain? It seems that the desire to get away from chemicals we ingest that are deemed “safe” by the FDA and EPA is a never-ending race. 

So, let’s get into it, shall we? Continue reading to learn the science behind why dish soap is not safe for use in your garden.

How the Myth Developed

The recent history behind using dish soap as a safe alternative to commercial insecticides is rooted in a desire to be kinder to the environment while still removing common garden pests. According to an article written by Linda Naeve, a program specialist for the Iowa State University Extension office, it all started about 15 years ago when, “a celebrity gardener promoted the use of all types of household products to green up a lawn.” An endorsement that may not be the best solution to your pest control problem. 

Ultimately those concerned about the environment and what they are potentially putting into their bodies had their hearts in the right place by spreading this method around as a “viable” solution to pest control without using a store-bought insecticide.

The Ins and Outs of Dish Soap

Dog being washed with superimposed warning label stating to not use Dawn dish soap on dogs.
If dish soap is considered toxic to pets (and it is!), why would you think it is safe for plants? Ill.: bulldogvitamins.blogspot.com

Let’s break dish soap down into its components. The most commonly used dish soaps (Dawn, Palmolive, and Ajax) have ingredients in them that aren’t great for our bodies. This may seem counterintuitive since we wash the dishes we use to use with these soaps. 

Two of those common ingredients that have gotten some news time lately are sodium laureth sulfate and sodium lauryl sulfate, or SLS and SLES as they are commonly known. SLS and SLES are surfactants, which we will cover further below, but these chemicals also contain measurable amounts of ethylene oxide and 1.4-dioxane. Both ethylene oxide and 1.4-dioxane are chemicals that take a long time to degrade and therefore remain in the environment long after they are rinsed down the drain. 

With this in mind, think about the homemade insecticides that are made of store-bought dish soaps. Even though you might imagine that the chemicals are washed away after thoroughly watering your plant or after a rainfall, the substances are actually still around. Only now, it is in the plants’ soil affecting your plants. 

With the potential of these chemicals lingering in your soil and potentially affecting your plants’ growth, is it still worth the risk of trying to use dish soap as an insecticide?

Why You Shouldn’t Use Dish Soap in Your Garden

Spraying plants with spray bottle
Be careful what you spray on your plants. Photo: freepik.com

Dish soaps are detergents that act through their surfactants. Returning to SLS and SLES, they are surfactants that dissolve the barriers between water and oils or dirt.

Your garden is full of what now? … Dirt, plants, water. 

These surfactants can’t tell what is good or bad in your garden, what needs cleaning and what doesn’t. While they may eliminate some insects that are pestering your garden, they have the potential to damage the plants in your garden.

Most plants have waxy coatings on their leaves as natural protection. Because surfactants naturally break down the barriers between oils and water, it can interfere with this protective barrier. 

Furthermore, dish soaps may also kill beneficial insects that help your garden flourish and would otherwise get rid of the very insects that you are trying to control.

So, What Can You Use Instead?

To avoid chemical use, you may have to let nature take its course. Allow insects created for destroying the insects that destroy your plants do just that.

Three brands of insecticidal soap.
You may have to purchase insecticidal soap, but at least it won’t harm your plants.

If that’s not for you, the best alternative may be a product from the store that will protect your plants and control your pest problem. Commercial insecticidal soap has gotten safer and is effective at pest control without harming plants. While it might not be your desired option for your pest problem, it is a viable, safe solution that will keep your garden thriving and isn’t the worst thing you could be putting into the environment.

You can check out more about what insecticidal soap is here. If you are interested in more gardening tips, you can also visit thegreenpinky.com

10 thoughts on “Garden Myth: Is Dish Soap Safe for the Garden and the Science Behind It

  1. I’ve been looking into how to make my own insecticidal soap and one of the more common ingredients (which I’ve never seen, but am gonna look for for the other hundred uses) is castile soap. Apparently it’s good for everything, but I don’t want scented soaps if the whole point is to have fragrant herbs in my house. However, I’ve gotta do something about all the gnats that are flying around my herb garden, so insecticidal soap will have to do. Hoping it works again. Never seemed to work long outside, but then again, so many plants, so much sudden rainfall (ugh). I’m giving it a shot for inside plants, because these bugs are driving me nuts.

      • and it seems to work quite nicely. Found a good recipe for the ratios last night (and these two bottles I bought will last me a long time). Hosed down the plants and soil with the sprayer and barely any gnats this morning. I was so relieved, and it doesn’t have an overpowering smell. I got the unscented kind but since they only had one bottle of that, i got the hemp almond kind, too, and that has a light smell. Still, glad it worked. I was sick of paying at least $6 a bottle when I was getting it before, and no guarantees it would be in stock. Now I can make gallons.

    • There is a trick for finding them. If you locate the “Search” button in the green menu on the left and enter “Garden Myths”, it will pull up most of them. I’m not sure I used “Garden Mythes” as a category way back at the beginning of the blog, so a few could be missing.

  2. What ever happened to good old fashioned horticulture?! I use no pesticides, not because I object to them, but because they are not necessary. Roses get aphid, but because they are pruned aggressively, they outgrow the aphid. Peach trees get peach leaf curl, but because they get pruned aggressively, they outgrow it. Scale and whitefly in citrus do not like good air circulation through a well groomed tree. Excluding ants inhibits the proliferation of scale. Well, I could get very carried away here.

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