Love those planters! We just started a "seed library" at the tool library, we're definitely interested in any sort of "found object" planters if you've got ideas

What I found works great is those large tubs/buckets that have oil or sauce in them. I've heard those large plastic buckets they sell large amounts of tobacco in work well, too. Any plastic that is used for consumables is good enough so it wont contaminate the soil or "leak" plastic into the crops. After a recent experience I would recommend to get new ones every 2/3 years if you leave them outside 24/7.

They do go brittle after about that amount of time. They are perfect for anything that needs deep roots or grows underground. Another one I would do is break wooden pallettes apart with a crowbar, trying to keep as much of the length of wooden 2x4's. You can make a flat U shape with those and screw it together with the rest of the wooden pallette you have left & use the square blocks underneath them to keep it from

having full-contact with the ground it's on. Because of how most pallettes are made, water will be able to drain out from the bottom unless you put a proper inner coat in the planter itself. If you leave it out 24/7, a wooden planter made from something like that will last about 2 years before the wood start breaking down. You can "extend" it's life to almost 5 years if you put a quick and simple varnish coat on it.

uuuhhhhh, I'm kinda trailing off. A neighbour of mine uses paint buckets and those mixing buckets you see small construction companies use. He uses it more for herbs and flowers. They seem to also work well, I can imagine you could leave those out forever in any weather.

Thank you for your interest! I hope this helps in any way! I love the idea of the Tool Library, I hope you've been able to help people get working on all the wonderful things from a little retooling of the yard to just small fixes in the house they just didn't have the tools for!