dishwashing liquid added to plant water

eileen_plantsJuly 25, 2006

I am reading a houseplants book by Jerry Baker who recommends adding 1 ounce dishwashing liquid per gallon to water used for watering plants. This is to allow the soil to absorb the water right down to the roots. Has anyone done this? It sounds strange to me, but I'm new to plant care. Does it work?

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tapla (mid-MI z5b-6a)

Well, surfactants (detergents) make water wetter & allow it to "seep" or flow into all the tiny places much more readily. It also tends to negate the effect of how Fe-containing molecules form on organic surfaces, which turns soils hydrophobic (water-repellent) as they dry to below about 30% moisture content.

Maybe it's just me, but I think that a 1:128 solution of H2O:detergent sounds pretty concentrated for use as either a topical or root drench. There are organic compounds in roots (oils eg) that are readily broken down by detergents, which I cannot imagine to be a good thing. A better strategy is to use a porous soil & water frequently enough to prevent a drop below 30% soil moisture and forgo the detergent.


    Bookmark   July 25, 2006 at 7:04PM
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Thanks, Al, I will take your advice...sounds a lot safer, not to mention saner!!

    Bookmark   July 26, 2006 at 5:14PM
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soundgarden(z8/ New Orleans, La)

I use dish detergent in my plant water all the time, as well as grapefruit seed extract, and my plants are very healthy and happy. In fact, a couple months ago when I was still in Colorado and we were having a drought, a bunch of people (including me) were squirting dish soap on lawns before watering them so the water would penetrate the roots more efficiently. I had the greenest grass on the block!
If you're worried but would like to give it a try, use plain old ivory dish liquid. I use whatever I have available. When I fertilize my houseplants I fill the sink with warm water, add fertilizer, dish soap and GSE and pour it on all of my plants. I used to have problems with gnats, scale, spider mites and mealy bugs, but since I started doing this I haven't had any of these problems.

Good luck, Annie

    Bookmark   July 26, 2006 at 11:08PM
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Anyone know if true soap (rather than detergent) would work similarly? I use a bit of Dr. Bronner's Magic Soap, which is a natural liquid castile (i.e. vegetable oil based) soap in my misting water to deter insects, and I have watered with it before to get rid of fungus gnats. So would this type of soap "make water wetter"?

    Bookmark   July 27, 2006 at 3:39AM
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farmerted361(zone 6 Western NY)

A cheeper way is to save all those little bits of hand and or bath soap and crush them down, and add them to a covered bucket 2/3 way filled with water. The soap will desolve in time, unless you help it along. Add water or soap to get it to look like old ivory dishwashing liquid, now its ready to use.

To use, add 1 to 1 1/2 cups per 2 gallons of water, and spray to clean off dust, help get rid of fungus gnats and other bugs. To use for watering plants use 1/2 cup of soap to 2 gallons of water. This can be used both indoors and out in the garden on everything. I use it on my Heirloom Tomatoes and I don't ever see bug damage!

To really control bugs I do the following:

This is what I do, firstly use softsoap water to control the gnats, using sticky traps work very well. But what I found really works best is to nuke the soil in a thick plastic bag that won't melt in the microwave for 10 minutes or so. What you want to do is to get it to boil and kill off everything! Once the soil cools down to room tempature, you can now replant the plants. When I get or buy a plant, I keep it away from the rest till I know its bug free, I spray it with softsoap water and then remove the soil that came with it and throw it away, then I use my own mix. This has been the only way,(For Me)I've found to keep the fungus gnats and other bugs from taking over.
Hope this helps, farmerted361:)

    Bookmark   July 27, 2006 at 8:14AM
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albert_135(Sunset 2 or 3)

I would agree with tapla, 1:128 is too much but I would not hesitate to add a quarter to a half teaspoonful to a gallon of water. I don't know any reason to do it unless you are attempting to correct some situation such as quick wet down some unusually dry soil, or as someone else above suggested, to wash off leaves.

    Bookmark   July 27, 2006 at 1:32PM
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korina(9b, Sunset 17)

You know that plant in the back that you missed a few times (ahem) and now it's bone dry and wilted and the water just runs right through? Add a few drops of dish soap to a bucket of water and drop the plant in, pot and all; the surfacent helps the water absorb into the soil.

I don't see why you'd need to add it on a regular basis.


'Butter wouldn't melt in my mouth. Well, it would, of course it would, but *very slowly*.' ~Wolf

    Bookmark   July 28, 2006 at 3:02PM
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Korina, I think I'll take your advice. WIsh I had learned this sooner! The book was written 20 years ago, and maybe soil mixes have come a ways since then. I won't be adding liquid soap on a regular basis, but for the situation you describe, I think it would be a good thing. Thanks!

    Bookmark   July 29, 2006 at 11:28AM
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I'm glad that there is a post about this!! I had a problem with an arcea (sp?) palm I got having fungus gnats and something spotty on the stems. I've been spraying it daily with a mild dish detergent/water mix and successfully got rid of the gnats and the spotty stems, but I was worried about the dish soap getting into the soil, but hey, I guess it's good for it! Thanks everyone! :)

    Bookmark   July 30, 2006 at 5:31PM
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I sometimes add a couple drops of dishsoap per gallon of water..but I do so more as a foliar spray. It's a great bug repellent, and if there are bugs such as mites, the soap will help rid them..Toni

    Bookmark   July 30, 2006 at 8:38PM
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I work at a greenhouse and we mix our own soil, mixing all the components; black dirt, peat moss, perlite, time release fertalizer, and a wetting agent that is essentially powdered soap. It helps with water absorbtion and helps keep the soil from crusting over as much. I guess I would feel alright about mixing soap into my water but like many have said you probably wouldn't need a whole lot.

If you just want to get your soil saturated you can simply put the container in the sink or tub and let the soil absorb all the water it can, this is also good if you are using clay pots because the clay is so porous that it will steal the water from your plant, so soaking them also allows for the container to get "watered". I usually soak the containers for different times based on container size.

hope that helped, sorry I went on so long.

    Bookmark   January 25, 2007 at 1:24AM
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I don't routinely use it but I have on occassion had potted plants dry out so bad the mix shrinks away from the side of the pot and water runs right off. A couple tiny drops of dishwashing liquid on the surface will allow the water to soak in and rehydrate the root ball.

    Bookmark   January 25, 2007 at 4:55PM
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Hello, um I'm writing report for my biology classes from experiment in which I watered plants with mixture of soap and water and I need some quotation to proof my results. The book eileen_plants mentioned seems suitable, but it is not available in my country, so I want to ask if someone could write here the quotation about watering plants with soap? It would be so much help for me

    Bookmark   September 9, 2014 at 11:14AM
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