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How to Get Rid of White, Fuzzy, Moldy Potting Soil

Updated on October 17, 2017
Joe Macho profile image

Zach's writing ranges from matters of gardening, cooking, aquariums and fish to more niche topics like coin collecting.

White, Fuzzy Growth in Potted Plants

All is fine and dandy until you wake up one morning to discover that your favorite potted plant is growing fuzzy white mold. Worried, you run to Google, type in "moldy potting soil," and you've managed to end up here. That's a good thing too, because I've got the answers!

That stuff is probably a harmless saprophytic fungus. Below, you'll learn whether or not to be worried, how to remove the mold naturally and safely, and a few proactive steps you can take to ensure that it doesn't return. The process is quick and painless, for both you and your plants!

Is Moldy Soil Bad for Plants?

The quick answer is no, that white stuff growing in your potted plants will probably not harm them. Although you don't always see them, molds and fungi are present in every organic gardening mix. In fact, many organic gardeners believe that "living soil" is the ideal environment for growth. So it's a sign of life, although it might not be one you want to look at, since it's not exactly pretty.

On the other hand, a saprophytic fungus might also be a sign that your plant is not getting what it needs in terms of sunlight, air circulation, and moisture. The mold might also be competing for nutrition with your plant, so it is also a sign that you need to pay attention to.

How to Remove Mold From Soil

If there's mold growing under your houseplants, or in any container plant for that matter, here's what to do:

  1. The first step is physical removal. Wearing a breathing mask, scrape off and discard the affected bits of soil.
  2. Lightly dust the soil with ground cinnamon. Cinnamaldehyde, the stuff that gives regular cinnamon its flavor and scent, acts as the perfect natural fungicide and prevents mold growth. Try to get an even distribution and remember that it only takes a thin layer.
  3. Do not water until the top two inches of soil are dry. For smaller containers (a gallon or smaller), wait until the top quarter inch has dried before returning to a water regimen. Use your finger to gauge moisture levels.

Potted plants are prone to mold. Impermeable plastic containers and pots without holes retain moisture.
Potted plants are prone to mold. Impermeable plastic containers and pots without holes retain moisture.

What Else Can You Do?

  • Never let pots sit in saucers full of water for more than 5 minutes. Drain off excess moisture.
  • Place plants in sunlight or strong artificial light to help them dry.
  • If you see any mold, take the plant outside for a day to expose it to natural light and air. When you bring it back in, choose a new home for the plant in a spot that is slightly more sunny and breezy.
  • You might also consider transplanting to a larger pot full of fresh dirt. Make sure you choose a pot with plenty of drainage holes.

Is it Safe to Use a Bag of Old, Moldy Potting Soil?

Sometimes, you may not use all the potting soil at once; later when you go to use some more, you discover that fuzzy white stuff has bloomed inside the bag. It might also be that you buy a new bag of potting soil, bring it home, and discover the same thing. The question is, can you still use that soil?

  • If you are transplanting, planting, or just replenishing dirt levels, the answer is yes. Before you use it, simply mix up the contents of the bag and work the white stuff back in with the dark. You might also add a little fresh compost. Cut the bag open and leave it outside, exposed to the sun and air, for a day or two, turning occasionally. You could also mix in some fresh compost.
  • On the other hand, if you're planning to sow seeds, you should NOT use that soil. Since the mold will compete with the seedlings for nutrients, it's best to give the new plants a fighting chance in some fresh dirt.

Is the White Stuff Growing in Your Potted Plants Dangerous to Humans?

If we see mold, most of us react by covering our mouths and running the other direction. But, although most mold-removal companies will try to persuade you otherwise, the mold in your potted plants is not particularly dangerous to humans.

On the other hand, if you are extremely sensitive to mold allergies, you might not want to take any risks. Some people have claimed that the spores trigger allergic reactions.

Outdoor container plants are less likely to grow mold, but it does happen. The plant likely needs less water and more sun and wind.
Outdoor container plants are less likely to grow mold, but it does happen. The plant likely needs less water and more sun and wind. | Source

How to Prevent Mold From Growing

Mold can never be totally eliminated. The truth is that mold spores are a regular part of soil and are normally harmless. The real threats to your plant are heat, humidity, and low ventilation. Under these conditions, mold spores grow into their adult fungi form and release even more spores. Indoor planters and container gardens are common hosts, as they retain more moisture. To prevent mold growth, follow the simple steps below:

  1. Don't Overwater. Overwatering is the main cause of mold growth in container plants. Soil that is constantly moist is much more likely to harbor happy spores. Water only after a quarter of the pot's total soil volume has dried out. For example, if your plant's soil is 8" deep, don't water it until the top 2" have dried out. For most indoor plants, watering once a week should be sufficient.
  2. Reduce Humidity & Increase Ventilation. Together, these two conditions create the stale environment in which mold thrives. By already not overwatering, you're also reducing the humidity, so to reduce moisture even further, place your plants in sunnier, well-ventilated areas or use a small fan to constantly push new air around the soil.

Is It Mold or Perlite?

Don't mistake the two: Perlite is a white volcanic glass that is used to improve drainage. It's not harmful to plants.

Final Word

Overall, mold in potting soil is very easy to treat. My one word of advice is to avoid the use of vinegar. Mold can survive the acidity, but your plant's roots may not! Cinnamon is a much safer and effective option.

Comments, questions, and suggestions are always appreciated!

© 2012 Zach

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    • profile image

      Trish B 2 months ago

      Thank you, I know what i'm doing wrong now and how to correct it.

      Many thanks

    • profile image

      Isabelle 2 months ago

      Hello! Thank you for this helpful information! I have a question I hope you can help with. One of my potted plants got infested with mold, I planted two kinds of basil. One of the basil plants was basically dead while the other seems to be fine. I want to replant the basil that is ok with a new basil plant, new soil and all. Using your cinnamon trick on the basil that was with the infected soil, would it be safe to have in the new pot with the new basil plant? Or should I have two separate planters?

    • profile image

      Alexi 3 months ago

      Not only did this solve my mold problem, but finally my "allergies" from the past few days make sense! I had forgotten about airborne mold spores... ._.

    • profile image

      David 3 months ago

      thanks for the advice

    • profile image

      Sandra 3 months ago

      Zach, I am glad I found your site. I will try the cinnamon treatment on my moldy plants. Thank you for the information!

    • profile image

      Margaret Hicks 6 months ago

      Hello, I live in an apartment on the second floor and really don't think that I have any light coming in the window and don't want to take a chance and put it outside with the kids or someone may steal it, and I'm not sure what part of the day there would be any kind of sunlight on the balcony (if any). Is it possible I could put it under a desk lamp that uses a 15 watt lamp (maybe a florescent bulb as it is a long bulb, not sure).

    • profile image

      Rusti 7 months ago

      Thank you! Easy to read and understand information, fast service. Loved this site!

    • profile image

      Sabrina 7 months ago

      Thank you so much for all the information!

      I got a whole planter with spinach full of furry white mold, I'm trying this!

    • profile image

      Linda Matz 7 months ago

      I think I am going to really like this site!

    • profile image

      Li 8 months ago

      Will try this

      Thanks

    • profile image

      Ryan 8 months ago

      My soil isnt moldy, but it has some kind of slimy substance on it. Any idea what it might be?

    • profile image

      Michele 9 months ago

      Thanks for the tip about Cinnamon, I'll definitely try this. I have several Anthurium potted plants side by side and only one displayed wispy white strings on the soil, which I figured were spiders, so sprinkled heavily with Orange and Lemon peel (Spice World). 1 week later, the entire top is looking more like mold. The are in bright light but not sun which will burn the plant, I have a TheraPure increasing ventilation and they look extremely healthy with lots of blooms. Does this sound like mold? What else can I do?

    • profile image

      Patricia Branagan Cannock staffs 11 months ago

      I had a new plant last week for a Christmas present( a Poinsettia) within days all the leaves dropped off, and the soil is already mouldy, does this mean than it was stored in the wrong conditions in the store. I will try your remedy. Thanks

    • profile image

      Betsy Bowen 12 months ago

      Our house cleaner told us that there was white mold on our orchid plant, so we took it out side and threw all the old dirt and mold away. Gave it a good new supply of Miracle Grow, cleaned the pot, washed the roots of the plant and repotted it adding the ground cinammon. My housecleaner saw it today and suggested I ask Google what to do. What did we do wrong that made the mold show up again. We water it from the cold water at the kitchen sink as we do the other plants and they do not have the white mold. This plant was given to me by my best friend who passed away in June and I do so want to keep it safe and flowering. Thanks for your info.

      Betsy Bowen at betsybow77@gmail.com

    • profile image

      constance 12 months ago

      i keep my organic potting soil in a tub with a lid and now everytime i open it the whole top is covered in white fuzzy mold. this has never happened to me before. will the cinnamon work in this condition and should i dispose of soil or remove mold and keep?

    • profile image

      Susan Johnson 13 months ago

      I love different ideas on how to take care of life with household products that are all natural I do have a question how often should we put the cinnamon in our plants once a month?

    • profile image

      Susan Johnson 13 months ago

      Thank you so much I also knew this trip and my plants are growing beautifully now!!!! keep sharing!!!!

    • profile image

      Ella 13 months ago

      This was very helpful! I am going to try the cinnamon trick, but another problem I am having is the mold is growing on the actual pot. Would this also be due to ventilation/lack of light? What kind of artificial light would be helpful?

    • profile image

      David O 14 months ago

      Cinnamon did NOT work for me

    • profile image

      Clara 15 months ago

      I put a fair amount of cinnamon on the earth of my large leaf plant was give to me when I lost my husband so don't know what it is called but it did have large cup size white flowers but I have transplanted it with the best earth and I watered it every two weeks now I am wondering if I can water over top of the Cimmon and how often should I water this plant ?

    • profile image

      16 months ago

      Would irradiated cinnamon work?

    • profile image

      Kathy 16 months ago

      Comment...I would like to know the cause of a powdery substance (from Flowers)

      on my peace lily houseplant.mmIt also has a grayish film around the plant at base of potted

      Plant. Are the two symptoms connected to the same problem? Also the lilies have brown

      colored spots on them that have worsened and turned a darker brown with larger spots.

      I have cut these flowers off along with the long stem. SOS here..I hate to lose this plant!!

      I will try the Cinnamon treatment you have suggested andTHANKYOU!!

    • profile image

      Sharinhall@yahoo.com 3 years ago

      What if you have brownish orange mold in your soil? It turns to powder wen u touch it. Will cinnamon work on this too?

    • profile image

      Jaimie G. 4 years ago

      I had heard that using a splash of sprite in your house plants helped with the growth, because of the sugars and such! Well, since I have done this, I now have white furry mold growing on the plants and they are looking VERY unhealthy!!! HELP!!!!

    • Joe Macho profile image
      Author

      Zach 4 years ago from Colorado

      Virginia - Yes, you can sprinkle the cinnamon over the soil even if your plants have already been watered. Just plan on letting the soil dry out a bit before you water again.

    • profile image

      Virginia 4 years ago

      I will be trying the cinnamon! I also want to know can you still sprinkle it even if you have already wartered your plants?

    • profile image

      anne arsenault 4 years ago

      most of my plants have mold thanks I will try cinnamon hope it works

      I never new what caused the mold thanks hope it works.

    • rbm profile image

      rbm 5 years ago

      Great tip, will definitely give this a try. Who knew that cinnamon could be used to get rid of mold! Pretty interesting.

      Good hub, voted up and useful.

    • Joe Macho profile image
      Author

      Zach 5 years ago from Colorado

      Since the mold typically only affects the soil, the green onions should be just fine to eat.

    • profile image

      Amanda 5 years ago

      Hello,

      I've got furry white mold growing in my potted green onion's soil. Is it safe to still eat the onions after the mold is removed?? Thanks.

    • livelonger profile image

      Jason Menayan 5 years ago from San Francisco

      I have this problem and ironically found your Hub via Google! I scraped the mold off, sprinkled a generous amount of cinnamon, and am waiting to see if it did the trick!

    • Joe Macho profile image
      Author

      Zach 5 years ago from Colorado

      @Elke - I'm not very familiar with Money Tree plants, nor is it easy to make a diagnosis without seeing the actual plant, but it seems to me you are correct. The white mold on the soil will most definitely affect new growth before the older established leaves. Along with the cinnamon, try to get a light/heat source that will dry the top layer of soil out a little quicker

    • profile image

      Elke 5 years ago

      I'll try the cinnamon approach. I have a "Money Tree" plant. The new growth reaches a certain point, then withers and dies. The mature leaves seem unaffected so far, but I blame the white moldy film on top of the soil for the stunted growth of the baby leaves. Am I right?

    • Joe Macho profile image
      Author

      Zach 5 years ago from Colorado

      nifwlseirff - That you must! Cinnamon works great and can also be used in other areas of the garden too! If your plants show foliage signs of powdery mildew, cinnamon can be used as a spray to control it. I wish you the best of luck.

      phoenix2327 - Hello again! The gardening bug is definitely running wild. As far as I can remember, Moss grows on soil because of moist and acidic conditions. I would recommend physically removing the moss and then sprinkling a little wood ash over the treated areas. The ash will make the pH swing up just enough to discourage future moss growth. Hope it helps you out.

      Lissie Loomes - Glad I could show you something new! You'll be amazed at how well it works.

    • Lissie Loomes profile image

      Lissie Loomes 5 years ago from Tasmania, Australia

      Thanks Joe for the cinnamon tip - hadn't heard it before but will certainly try it on my indoor garden when necessary.

    • phoenix2327 profile image

      Zulma Burgos-Dudgeon 5 years ago from United Kingdom

      You hubs are well timed as my mind is turning to a bit of gardening this weekend. I'm wondering if you might have any tips as to moss growing on top of the soil. Have shared this on Twitter and FB.

    • nifwlseirff profile image

      Kymberly Fergusson 5 years ago from Villingen Schwenningen, Germany

      I must try cinnamon! I've been plagued with a little white 'film' on my potted plants' soil for months, which quickly grew back when the surface was scraped off. Thank you!