I think it depends on the container. I believe the toxicity of polyurethane peoducts varies greatly by the type of polyurethane. You'd probably need to know specifics about the foam to make an educated guess or do more research. Not sure it's something I'd try without knowing for sure.

Thanks!

They are perfectly safe to grow potatoes or any vegetables in. PU foam is damn near completely inert and there is no mechanism for the plants to take up anything that could be a problem.

The same foam is used as mortar in koi ponds because it is so nontoxic.

Even better! Thank you.

How about white Styrofoam coolers? I'm amassing quite a collection from food shipped frozen.