How to store potting mix w/o molding?

I bought some Jiffy seedling mix it looked fine after opening and 4 days later my beans are sprouting.No mold with soil in pots with sprouts.
I stored it in my closet decided to plant a few more beans and after 5 days a light green mold on surface had appeared?

I’ve heard if you spread out potting mix on a black plastic tarp and let sun hit it all day it kills mold,bugs,etc… that might have started during storage even if unseen?? Any truth in that ?

Yes, that will kill much of anything growing in the soil.

Oh yeah, turn the soil over, you want all sides of it to get plenty of exposure to UV light from the sun, this will work well for mold. The mold that started growing in your soil, there are likely spores of that mold already in your grow area and on your plants. Fungus/mold spores are everywhere and so it’s more a matter of inhibiting them than eliminating them, and they don’t usually become a problem unless the environment is right for an outbreak. Fungi doesn’t like light or air, especially lots of oxygen, so keeping things well ventilated and dry is a must. High humidity is a fungus’ best friend.

Algae. Mot mold. Mold is not green. I find this interesting, because in all my years of growing; I have never had an environmental issue with starting mix. :mrgreen:

Actually different kinds of mold can be different colors, that green stuff that grows on old bread, that ain’t algae, it’s mold. Bud rot mold is usually grey, but it can have hints of green in it too. The mold that grows on soil will most often be gray, but it can green or even white. The mold in his bag was probably from the soil mix being too wet/moist and the environment where it was stored a bit on the warm side. The mold spores could’a come from anywhere, even from the nursery the mix came from, or it could have already been residing in the closet maybe because of any of a number of reasons. I remember growing up in a home that was “swamp” cooled or cooled with a evaporation cooler. The humidity levels would get so high during our summer hot rainy season that the cooling affect would kinda stop working and leather goods stored in the closets, like belts, boots, leather luggage, etc. and such would often develop green mold growing right on the leather.