I have many pots on my back deck and it would be handy to keep the potting soil mixes there as well. I'm thinking of purchasing some large storage bins (I use one of those in my garage to keep soil mixes in). Is there a downside to keeping soil in such a container on my deck? I just don't want any bad bacteria or mold to grow there that might harm the plants later. Thanks.

I keep potting soil mixes in a large storage container outdoors...one of those big plastic totes available at any hardware store. Sometimes if I see a lot of condensation on the underside of the lid I leave it open for a day to dry out, but I haven't had unpleasantness in them. It doesn't stay undisturbed or unused for very long however; maybe a couple of months max in the coldest part of winter. It is in a shaded location.

I would be more concerned about container sitting on the deck than the contents. If the container causes moisture to stay underneath, that could cause a wet spot & premature deterioration of the deck. When I do buy it, I keep bags of potting soil just about anywhere outside until they are used, as long as it can't get rained on.

Ha! I often forget about moisture issues. 🌵

Yeah, probably not an issue where you are.

Well, rotting a wooden deck with consistent moisture can happen in any climate, but admittedly it's not the first thing that pops into my head

Good point about the moisture getting trapped underneath the container. Maybe I could just put it on some short plant stands or caddies to keep it off the wood. Thanks to all!

Is there a downside to keeping soil [container media] in such a container on my deck? There is if the medium is wet or moist.

With the containers covered and the medium wet, waste gasses will soon displace the oxygen in the container. Hydrogen sulfide, CO2 (in the root zone), and methane are examples of waste gasses. The organic acids generated under anaerobic conditions can/will seriously lower the pH of the medium, which in itself is a problem that requires a good deal of leaching to rectify. Generation of organic acids in pine bark is why bark destined for use in container media is piled high in wind rows and turned regularly with heavy equipment to aerate/ oxygenate the material to prevent significant reduction in pH from occurring.

Another moist/ wet media issue that arises when the medium includes controlled release fertilizer (CRF) products, like Osmocote. Release of nutrients from CRF prills is largely temperature driven. The process of composting/ decay of organic materials is exothermic, meaning the process gives off heat. Supplying the moisture essential to soil organisms hastens the composting process which releases heat which increases the release rate of the fertilizer which increases the population numbers of soil life, ad infinitum, until the fertilizer prills are empty of nutrients. This can create plasmolysis/ fertilizer burn; so it's good to avoid storing media containing CRF prills, or use it until it's been leached.

Al

In a plastic bin on my deck VS in a plastic bin in my barn. What's the difference? If your medium is wet or moist, it doesn't matter where you keep it, it will mold. Most of us (maybe only me?) keep our soil dry until we use it.

I would be more concerned about the plastic bin being degraded by the elements.

That's a good point, plastic storage bins do not last long if exposed to sunlight. Many other plastic objects too.