Rooting Plants With IBA: Myths, Facts, and the Why it Works

I was looking around the internet, searching for how rooting hormones work in willow cutting solutions, and I stumbled onto a video by Fraser Valley Rose Farms on YouTube. In the video, Jason explains why things like Aloe Vera, Cinnamon, and yes, even willow solutions, don’t work nearly as well as commercial rooting powders. I watched all this with a few willow strips sitting in a jar in my kitchen, and I felt that oh so uncomfortable cognitive dissonance kick in. I wanted him to be wrong. But his reasoning was scientific, and so I went on my own journey in exploring rooting solutions determined to find a way to make my own–even if that means I need to find a recipe that is essentially the same as a commercial powder. Because I can.

Before we dive into hormone powders, I want to talk about safety. Jason touches on the safety of IBA (Indole-3-Butyric Acid), remarking that he has done personal research with it and feels comfortable using it. He even made a video explaining why he feels that it is safe, which was a great starting point for me. He explains that while it could be acutely toxic, this toxicity is dependent on consuming pounds worth of IBA, which would have to be intentional. He remarks that the real danger of rooting hormone powders lies with an inactive ingredient in it: talc. Talc is known to cause issues with breathing, eye irritation, and is often contaminated with asbestos, a known carcinogen. So, if there’s anything to fear in commercial rooting hormones, it’s not the hormone. Our bodies quickly break IBA down into harmless constituents, and its found in many natural foods. That said, I’m not super comfortable with talc due to its link to cancer, and if at all possible, I’d like to avoid it. I made a note here to come back to what other inactive ingredients could be used in talc’s place, and why talc was preferred.

White willow trees, aka Salix Alba, produce an abundance of Indolebutyric Acid, a natural IBA, which makes them incredibly easy to propagate in either soil or water. It makes sense why so many people swear by and use willow water to speed up propagation. However, cutting up willow whips and sticking them in water isn’t going to produce a good rooting solution. In fact, Garden Myths explains that “IBA is not very soluble in water, with a solubility of 250 ppm (at 20 °C). This is the highest concentration that you can get, assuming perfect extraction” (Pavlis). For reference, Jason says this comes out to be about a quarter of the strength of the very weakest rooting formulations sold commercially. Many plants will root without any rooting hormone at all, and this low of strength rooting solution could be seen as useful for speeding up the rooting process of such plants. However, for more difficult to root cuttings, it’s not nearly enough to stimulate root production in any meaningful way. Jason says that on a hard to root plant, willow water is “about 40 times too weak to do anything”. It’s also unlikely that you’ll even get a solution with that small strength of IBA, and you can’t really measure how much you’ve extracted either.

Additionally, alternatives like honey, aloe, and cinnamon do not contain rooting hormones. Instead, they have been used as a means to prevent rot or mildew growth while a cutting is propagated. Unfortunately, this isn’t an issue you can prevent by coating the outside of your plant with an antifungal material. Rot is caused by an imbalance in heat, light, humidity, and soil, according to Jason. If these things are well-controlled, there will be no need for cinnamon, aloe, or honey. Finding the right growing conditions for your cutting will greatly reduce your chance of rot. Unfortunately, these tricks for rooting plants just don’t cut it, and may even hinder your plant’s success. For example, some people have tried to root plants in bananas, leading to dead cuttings and moldy fruit.

So, how are IBA based rooting hormones made? I took a look at this site for scientific pursuits, Sigma Aldrich, and found out these important things:

  • Indole-3-butyric Acid is best dissolved in ethanol or sodium hydroxide solution 1N *, then diluted with water
  • *1N refers to the fact that 1 gram of solute to one liter of solution is being used
  • IBA was recommended to be stored at 32 degrees Fahrenheit, or -0 degrees Celsius in liquid form
  • IBA was recommended to be store at 35.6-46.4 degrees Fahrenheit or 2-8 degrees Celsius in powder form
  • I still had no idea what I could replace talc with if I wanted a powder
  • I still didn’t know why talc was used in the first place; is it only used to evenly distribute the IBA in its powder form? Did it have any preservative effects? Is it acidic/basic/does the pH matter here?

It was at this point that I decided I was thoroughly confuzzled.

I did what every desperate DIYer does; I hopped onto YouTube. I found a few videos, one of which used cornstarch in place of talc, but I wasn’t sold yet. They didn’t really explain how they chose it, only that they had. I later read that Hortus, a brand that sells several forms of IBA, does mention that you can create a gel with cornstarch and water along with their water soluble IBA. IBA is a very stable chemical in powder form, and although heavily debated, has been said to last for ten years or more (Hodgson). It seems like the easiest way to prepare this would be to buy powdered IBA and heavily dilute to no more than 1% IBA to 99% cornstarch. Then you could tap some powder out and dip the ends of your slightly moistened cutting into it. I had a very hard time finding how IBA was synthesized, and without proper information and safety guidelines, I don’t feel comfortable extracting or synthesizing IBA in my kitchen, at least not at this point. So that automatically puts a damper on my plans to just extract a natural IBA and make this powder from scratch.

If I bought IBA in a powdered form, I could dissolve it in ethanol and dilute that solution further in water to use as a rooting hormone for my cuttings. If I chose a water soluble option, I might not even need the ethanol. According to Garden Fundamentals, once you prepare a diluted liquid concentrate, you’ll need to use it immediately. You can’t save dilutions in the fridge or pantry like you can powder. Without any preservatives besides the ethanol, I’m unsure that the IBA, after mixed into its first solution of ethanol, would retain its function over time. It seems that most premade liquid concentrates last anywhere from 1-4 years when stored in a dark, cool area, but I couldn’t really determine why or how. I’m guessing that the stability of IBA paired with a dark, cool location keeps it effective for years, but I’m not a chemist.

So, other than buying IBA and diluting it yourself, there’s not really a way to DIY an auxin powder. I can safely say I did my due diligence in seeking out a way to create one all by myself, but I think I’m invested at this point. I wonder if anyone has placed a ton of willow cuttings in alcohol or ethanol? I couldn’t find anything on it specifically, but several of the solutions contain alcohol which is diluted or the cuttings are quickly dipped into it (alcohol isn’t good for plants, but 5 seconds seems to be okay for the IBA solutions). This topic is definitely something I’m interested in, and while I’m sad my willow water won’t do much good, I’m glad to be learning more.

Before I sign off, I want to mention that IBA is not the only auxin that promotes root growth. I saw NAA mentioned quite a few times, so maybe I’ll have better luck researching that one! And if not, well, I’ll learn some more! I’ve already got some new ideas for better stabilizing the environment of my cuttings, and that’s invaluable knowledge!

How do you ensure your cuttings thrive? Do you have any tips or experience with hard to root plants? Have you successfully cultivated any without the use of a rooting hormone? Let me know in the comments! Don’t forget to share and like this post so more people can see it! I’ll see you in the one. Bye!

Places to Buy IBA and Rooting Hormone

References

Croutch, J. (2020, September 26). Rooting Hormone vs. Homemade DIY Alternatives. YouTube. https://www.youtube.com/watch?v=R9aPvJIHsYk&ab_channel=FraserValleyRoseFarmFraserValleyRoseFarmVerified.

Croutch, J. (2020). Is Rooting Hormone Safe? YouTube. YouTube. https://www.youtube.com/watch?v=rFFYKanfudw.

Pavlis, R. (2019, November 24). Willow Water Rooting Hormone – Does It Work? Garden Myths. https://www.gardenmyths.com/willow-water-rooting-hormone/.

Schmidt, L. (1993, May). ROOT SETTING HORMONES. VEGETATIVE PROPAGATION. http://www.fao.org/3/ad224e/AD224E10.htm.

Hodgson, L. (2019, January 10). How Long do Rooting Hormones Last? Laidback Gardener. https://laidbackgardener.blog/2018/12/21/how-long-do-rooting-hormones-last/.

Hortus USA. (n.d.). Hortus USA: IBA methods. http://www.rooting-hormones.com/IBAmethd.htm.

Sigma Aldrich. (n.d.). Growth Regulators – Plant Tissue Culture Protocol. https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/cell-culture-and-cell-culture-analysis/plant-tissue-culture/growth-regulators.

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