I sowed a bunch of tomato seeds in soil blocks last week, and I put a humidity dome on top for 2 days, and when I pulled off the domes, I saw a ton of white feathery fungus and some grew mold. I have never used domes before and never had an issue with germination, but figured it could only help (guess I was wrong there)!
I removed some of the worst blocks, and sprinkled cinnamon on the remaining blocks. It’s been a few days and some seedlings are starting to sprout. I‘m still a little worried about problems down the line – could damping off be a concern? Could something else still lead to these plants not making it? I could sow another back up batch, but should I try and see what happens with these? Or am I missing something and should actually consider throwing these away and fully starting over? Or am I ok?
by Due-Coffee9582
13 Comments
Yes
I wouldn’t worry any more. Let it dry a bit. You already removed the worst ones. I would have re-used that soil later as well.
My only fear would be mold on the seed which would cause no germination.
But im no expert.
Pull all of the moldy blocks (Edit: sorry missed you already said/did that).
Make a dilution of chamomile tea to lightly mist the remaining blocks (acts as a mild antifungal). Remove the lids, and then monitor closely, aiming to keep the blocks lightly damp, but not wet.
Overly moist but completely fine. There are mold spores everywhere, literally.
Put a fan on your blocks. This will dry the soil out more, so be cognizant of that, but it will inhibit further mold growth.
Mold is not an issue technically but the conditions that allowed mold to grow are an issue.
What kind of soil are you using? For seedlings, a sterile seedling mix is best. This will reduce mold the most. I use a peat, coir, perlite, vermiculite mix.
Too much water, the blocks look awfully wet. Wet soil blocks usually will have all the air pressed out of them. This will make it hard for roots to grow. Soil blocks should be damp, not wet, when made and lightly sprayed after seeding. Id get a fan on them to pull out some water and leave the tops off. They don’t need the extra humidity when they’re that wet.
It was definitely not the dome that caused this but they did help the mold grow. I’ve used domes for 20 years and never have had mold growth though. As soon as seeds start germinating I move the dome askew to let air start coming in, and after half the seeds germinate I remove the dome completely.
Damping off risk will definitely be increased in this environment. The best way to mitigate this at this point (and also at seeding time) is to cover the soil with a layer of vermiculite. Damping off only occurs at the soil line, vermiculite on top will prevent it 100% of the time. When I plant my seeds, I plant them on the surface of the soil and top with vermiculite instead of more soil, to the depth the seed requires.
One last thing, the mold being aired out in your house will give off spores. If anyone has an allergy to mold or penicillin, then best to toss them if it will bother them. Most people will be fine though, as there is already mold spores in the air of most houses. White fuzzy mold is usually fairly harmless.
I can’t tell from the photos if you have a fan. Do you have an oscillating fan blowing over them? That will help once you start over.
Soaking the soil with a diluted hydrogen peroxide/water mix should kill the mold spores without harming the plants. Drop all the old wives tales/woo woo stuff like cinnamon and just rely on chemistry. Hydrogen peroxide is harmless to plants and breaks down pretty quickly into water and oxygen. Cheap and extremely effective. Also useful if you get fungus gnat infestations
Is that considered mycelium like In My compost?
Sprinkling cinnamon over the top of the blocks can help drive away mold
Mold shouldn’t affect germination. You could sprinkle with cinnamon to get rid of it, but not necessary. As others have said, your conditions are too wet/lacking airflow.
I find sprinking of cinnamon powder does the trick plus acts as nice fertilizer
Scrolling by I thought something absolutely diabolical happened to your tray of brownies 😭😅