My thought is it would be fine. Might boost the iron a bit. But that would probably be a good thing.

Just make sure they don't get set anywhere that will leave a rust mark. :-)

My grandmother used to plant things in coffee cans with the bottoms cut out, burying them up to about an inch from the top, and leaving them to rot in the ground, so I don't see a problem

abbidoo why would she do that

Yes, I'm curious, too Abbidoo. Why did she do that?

Maybe she did that for some of her more invasive plants, like peppermint, so it would stay where she wanted it?

I plant bulbs (sometimes) in a tin can with the bottom cut out to protect the bulbs from burrowing creatures such as moles. Cutting out the bottom maintains drainage.

My grandmother potted plants in Maxwell House and JFG coffee cans but only for plants that were outside the house, i.e., on the steps, on the porch bannister, on the sunporch. The rust wasn't necessary, as I recall.

Ray