Tissue box cubes:
You've probably all done this already, so this is really a follow up on how well it works. I saved all my tissue box cubes this year to use as pots to transplant tomatoes plants into.
I know they can be planted and will rot, but I prefer to open them, which is very easy;
And, rather then pulling them out through the hole, tear it. Very easy to plant and has a grapefruit sized root ball mass of dirt. Don't think they realize they were moved.