Mold on Soil...

iheartroscoe(Zone 5, Northern IN)April 11, 2008

I'm new to starting seeds indoors and I just started some vegetable seeds a couple of weeks ago. I noticed a white colored mold on the sides of my peat pots and was hoping this was safe around the vegetables.

I looked up some suggestions on how to get rid of the mold, but nothing I saw applied to vegetables. Is the mold because of the peat pots? I was thinking that maybe I should have used plastic pots.

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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

It is a chronic problem with peat pots. Most folks tend to keep them way too wet and that encourages the growth of the fungus.

If you let them dry out some it will die off or you can mist it with a 10% hydrogen peroxide and water solution. It isn't normally harmful to the plant unless it gets overwhelming. It also helps to have a small fan circulating air in the area of the plants. Especially good for the seedlings and helps keep the fungus under control. Remember, fungus needs moisture and heat to grow - dry and cooler temps kill it off.

Next time - go with plastic. ;)


    Bookmark   April 11, 2008 at 10:09PM
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iheartroscoe(Zone 5, Northern IN)

Thank you for the suggestions!

I think I learned my lesson with peat pots :)

I'll let the soil dry and get a small fan for air circulation.

Thanks again!

    Bookmark   April 11, 2008 at 10:34PM
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I've got mold too, but it's time for me to thin and pot up my seedlings. I can just throw out the wasted/wet peat pots and the soiless starter mix and just plant the seedlings in plastic 72 ct cell packs with miracle grow potting soil, right?

    Bookmark   April 15, 2008 at 4:54PM
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until the fungus sporelates we don't really know what type of it is, a good deal of fungus mycelium (think of it as fungal roots) grows out white. However, the two most common types of fungal contaminates you'll get from using Jiffy Pellets or Peat Pots is going to be trichoderma (forest green mold/ "the mean green") or cobweb mold (I forget the latin name).

Cobweb mold is responsive to a direct shot of 3% H2O2 (not diluted) however trichoderma will take that peroxide with stride and spit in your face for the effort. You'll know which is which within a day or two when it begins to spore. The cobweb will start to turn grayish while the trichoderma gets it's namesake green spores on top of it.

Both of them can be responsible for damping off disease if not contained because, as they grow through the soil, the mycelium completely consolidates control over the soil and literally drowns out the roots by preventing oxygen from reaching the roots. Both plant roots & fungus require oxygen to survive, however both seedlings and fungus spores favor elevated CO2 levels during incubation. In other words, you can't make a condition ideal for one without doing the same for the other.

The best advice, as digdirt suggested would be to increase the fresh-air exchange in your greenhouse dramatically. Don't use the "mini-greenhouse" covers and keep some kind of fan blowing on your pots and you'll go a long way to preventing these two molds from settling in on your plants.

As for temperatures, however, both trichoderma and cobweb mold thrive in temps between 45-98(F) so it's not so much "moist and warm" conditions, it's just moist. Randomly, many "snow-molds" - which infects lawns - have ideal incubation temperatures of 20-40(F).

To prevent the problem in the future, you can avoid peat based soils and switch to coco-coir (technically a more renewable resource anyways) instead. Some of the hydroponic stores sell coco-coir that comes pre-infected (by design) with specific strains of trichoderma which are designed to ward off more aggressive contaminate molds but they, themselves have a shortened lifespan and don't have the strength to consolidate control over the entire substrate (soil).

Either way, peat or coco-coir, the safest bet - although a hassle if you haven't got the equipment - is to steam pasteurize the soil before planting. All contaminate molds are mesophilic and cannot survive tempertures past the 130+ (F) mark so placing the soil into a steam bath where the internal temperature of the soil reaches 140-160(F) and stays there for about 45-60 minutes will kill off all harmful microbes while leaving the beneficial, thermophilic, microbes intact.



for the last couple years I've gotten interested in mycology and taken a hand at growing organic shittake and baby portabella mushrooms indoors. Those two molds are HUGE++ contamination vectors.

    Bookmark   April 15, 2008 at 5:22PM
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Another method I'm using more and more is the coffee filter and baggie method. I avoid peat and coir and soil-free mixes and transplant the germinated seedlings straight into fast draining soil mixes in 4" pots. I do mist with diluted H2O2.

    Bookmark   April 16, 2008 at 2:34AM
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I had the same problem with white mold growing in the dirt in my peat pots. I watered my seeds and took the plastic cover off. The mold went away without any treatment and my vegetables and herbs are growing well now. I am wondering if they will still be safe to eat?

    Bookmark   April 27, 2011 at 12:10PM
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Would you please describe the coffee filter and baggie method?

    Bookmark   May 2, 2011 at 5:39PM
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