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House Plants/Potted Pothos soil problem


I have had a pothos in my living room for a few years. A couple years ago I noticed when watering a scummy film with a chemical smell would rise to the top and float on the water. I kept trying to water it out but each time it was there. A year ago I re-potted with new potting soil (Miracle-Gro)and now it's doing the same thing again. Can this be from the plant pulling toxins out of our environment and it is coming up in the soil? I know they are known to clean interior air but this is really nasty.  Any ideas for me?  I'm ready to re-pot again but thought I'd get some expert advice first ;)  Thanks!

Hi Mary Lou,

Any chemical removed by the plant from the environment would never be visible, so that is not what you are seeing.

There are three possible sources of the scum you are seeing - the soil, the water you are using or the material the pot is made from.

Miracle Gro soil is often infested with fungus gnat larvae, but I have not heard that it is contaminated in any other way. Water quality is important. If your tap water is on the hard side (high mineral salt concentration), then that is likely to be the cause. If so, use filtered or distilled water instead. And if you have been adding fertilizer, stop. Make sure you are allowing the top quarter of the soil to dry out before adding any water.

I don't know what kind of pot your plant is potted in, but certain metals can interact with the chemicals in the soil and cause the problem. It is also important that the pot is relatively small and has a drain hole that allows excess water to drain out.

Finally, make sure no one is adding anything to the soil. I know some folks add beverages (coffee, tea, soda, etc.) to their plants and that is NOT a good idea. Pets have also been known to use plants as a potty.

Please let me know if any of this is unclear or if you have any additional questions.

I have written an article on Pothos care that I will email email for free to you (or anyone else) who emails a request to me at

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Will Creed


I am the only expert in this category with professional hands-on experience and knowledge of all indoor plants. I can answer questions regarding light, water, fertilizer, repotting, pruning and humidity and temperature requirements. I can identify plant pests and provide information on safe, effective treatments. My answers are based on 35 years of professional experience and scientific research and are clear and easy to understand. I do NOT use search engines to find answers to your questions. If you read my previous posts here, you will get a good idea as to how thorough and professional my answers are.


I have over 35 years of professional indoor landscaping experience caring for plants in homes, offices, building lobbies, stores, restaurants, and other adverse environments. I have written extensively on the care of indoor plants, including a 260 page book. My specialties include Ficus trees, low light plants, repotting, pest control, and re-blooming holiday plants. Be sure to check my ratings and nominations to learn why I am the top-rated indoor plant expert. I am the only House Plant expert consistently ranked in the AllExperts Top 20.

BA, Amherst College

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