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I recently germinated some coffee beans (soaked in water until a root appeared), and planted them in sterilized soil. I only lightly covered them in soil (based on this answer), so the tops of the beans were visible.

A mere three days later, a coating of white fluffy mold appeared most of the beans! The soil remains clear, presumably since it was sterilized.

My question is: Once mold has grown on a seed, does the seed have any chance of surviving? Or are these doomed?

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Mold can be lethal to seeds/seedlings if left unchecked. I germinated corn seed at one point, just to the point of root emergence, in wet paper (this was going to peat pots in the cold frame, and from there to the garden under cover, for a late May harvest).

Out of the 2 lbs of seed, about 2/3 of them developed mold just as the root began emerging. these were separated, and treated with potassium bicarbonate before planting, in the peat pots (which were then drenched with a biofungicide (Bacillus subtilis) at the first watering). I got an 85% healthy germination rate from these, which is not bad considering the conditions.

Out of the seeds that did not grow mold, I only got about a 20% germination, which I am guessing to be from mold forming after planting. Looking back I probably should have treated all the seeds against mold at the time they were planted.

Obviously this experience wasn't dealing with coffee beans, but I think it is useful experience for a lot of pre-soil germination when dealing with fungus.

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    This is exactly the kind of generalizable data I was looking for - thanks! – John Walthour Nov 15 '16 at 19:27
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NO. Mold or fungus on seeds does NOT always mean the seed is compromised. Check your potting soil bag and its contents. Did they include bacteria or mycorrhizae? Very cool potting soil but white mycelia is very common on soils, even sterilized soil. You WANT life in your soil. I read this article and felt well, it was a bit out there. Sorry, most seed needs darkness to germinate well or at all. Most people bury their seed too deeply. Throwing seed on top of the soil not only gets eaten by animals but gets dried out where the food IN the seed isn't useable.

I don't think this is MOLD on your seed. Just mycelia of fungus trying to thrive in your new, sterilized soil. I would certainly 'fruff' up the top of your soil now and then. Make dang sure you've got decent drainage (usually raised beds out of doors) don't over water, don't over fertilize. What are you doing for a watering 'schedule' and fertilizing? Please send pictures, this is all a huge guestimate based on experience. This article is in no way helpful for new gardeners, MY opinion. Let us know what you think...

  • This really doesn't answer the question - the question asks about the lethality of mold, or fungus in general. Have you seen seeds grow fungus and survive? That kind of observation would be an answer to the question. – John Walthour Sep 2 '15 at 12:43
  • Welp then, please send a picture of what you are seeing. Can you wipe the fungus off and the seed coat is still shiny? Seed coats are pretty tough for a reason. I am going to take ANOTHER guess and say your seeds are still viable. Soil temperature should be 60-70 degrees...that'll help. Did you cover the seeds with a plastic dome or plastic wrap to ensure the seed doesn't dry out? Yes, I've seen mycelia on seeds when a bunch got wet, I threw them out on soil as organic material and they all grew. I always plant seeds in soil depth at twice the size of seed. – stormy Sep 2 '15 at 17:09
  • The question says the seeds have already germinated but now have a fungal growth. – Graham Chiu Mar 1 '16 at 19:39

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