Ask a Question forum: white growth on top of dirt in seedling pots

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Name: Robyn
Minnesota (Zone 4a)
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robynanne
Jun 12, 2016 10:36 PM CST
There is a hard - almost crusty white.. something.. that seems to be taking over the surface of my seedling pots. It started in one and gradually showed up in a few more. It is water resistant so when I water the plant, it pools on top of the substance and gradually soaks in. I can use a knife or anything really and break it off, but it shows up again the next day. They are in those degradable seedling pots and those are inside cheap plastic pots just while I harden them off. As I've taken some plants out to put in the ground, I noticed that the degradable pot itself had the white growth and the dirt inside the pot had green or white also. I'm assuming (hoping) that whatever it is will vanish upon putting them in the ground and I won't have to worry about it again - it was probably from those cheap plastic pots and the degradable ones just creating a hot, wet environment in the sun.

That said, what IS the stuff? I google white growing on seedling pots and get fuzzy white fungus results but this wasn't fuzzy. It was crusty and made the water pool on it. The first day I saw it was right after I had sprayed some neem oil in the garden. I didn't use it to spray the seedlings but I figured somehow I must've gotten some on the surface of that one plant and it did that. I've since decided that it had nothing to do with the neem at all.
Name: Daisy
Reno, Nv (Zone 6b)
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DaisyI
Jun 12, 2016 10:42 PM CST
Welcome! to NGA

It could be a slime mold. Do you have some photos you could share? Also, could you update your information to include your location? It will make it easier for us to answer your questions if we know were in the world this stuff is growing.

Daisy
Name: Robyn
Minnesota (Zone 4a)
Seed Starter Vegetable Grower Herbs Enjoys or suffers cold winters Tomato Heads Garden Photography
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robynanne
Jun 12, 2016 10:48 PM CST


Thumb of 2016-06-13/robynanne/559e83

Actually, I do.. Didn't think I had taken any. In that photo, on the far left you can barely see the corner of one container that has the white. Then two that don't.. then another one that does.

Thanks!

I'm in MN.
Name: Sue
Ontario, Canada (Zone 4a)
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sooby
Jun 13, 2016 4:18 AM CST
Welcome! Can you tell us what planting mix they are growing in, are all plants in the same? Do you water with hard tap water? Third question, is there fertilizer in the water? Salts can accumulate on the surface although it looks rather excessive for that. Can you get a closer picture?
Name: Robyn
Minnesota (Zone 4a)
Seed Starter Vegetable Grower Herbs Enjoys or suffers cold winters Tomato Heads Garden Photography
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robynanne
Jun 13, 2016 6:04 AM CST
Unfortunately, no closer pictures. Once I realized it wasn't the neem, I started getting rid of it and there's nothing to take pictures of right now. (Fingers crossed that it stays that way. It has been a few iterations of scraping it off. )

That slime mold suggestion seems spot on, when I looked that stuff up. Like tiny crystals, almost.

They are all in the same mix. Part compost, part potting soil, which does have fertilizer in it. The pots themselves were the only difference. They were all in those plantable pots, but some of those were in those nice breathable brown round ones and when I ran out of those, I put the pots in the cheap plastic ones. The cheap plastic ones were the only ones to grow the stuff.
There is no fertilizer in the water, and usually I just use tap water though sometimes I get it from the rain barrel.

Thanks!
Name: Sue
Ontario, Canada (Zone 4a)
Daylilies Birds Enjoys or suffers cold winters Native Plants and Wildflowers Butterflies Annuals
Region: Canadian Keeps Horses Dog Lover Plant Identifier Garden Sages
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sooby
Jun 13, 2016 6:53 AM CST
Glad you may have your answer. This is what salts look like on the soil surface:

http://www.coopext.colostate.edu/4dmg/Plants/improve.htm
Name: Christie
43016 (Zone 6b)
Plays in the water.
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cwhitt
Jun 13, 2016 8:29 AM CST
I am also thinking it could be mineral deposits from your water.
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Name: Dnd
SE Michigan (Zone 6a)
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DogsNDaylilies
Jun 13, 2016 8:38 AM CST
I will also add that I think this is related to hard water or treated water. We have hard water where I am at and this happens to me at times, too. We treat our water with potassium chloride, so i haven't figured out yet if this happens when my water is hard (i.e. my water softener is low on water softener) or because it has been softened (I.e. the potassium chloride causes the white buildup). Or both? Shrug!

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