[Pollard]

Untreated wood lasts a couple of years here. I saw a video of a guy who experimented with molded concrete sides using different mixes trying to make them as light as possible. Ended up with a foam-crete type of thing.

The more I think about raised beds with sides, the more it seems like too much work. Since I have heavy soil, raised beds aren't a bad idea to help with drainage but I think this style is easiest.
(misc pic found on web)

Maybe with a little wider pathways. If I make 3 inch spacers for the wheels on my baby tractor, it would be 30 inches between the tires and would be easy to make and maintain these. Looks like 100 foot but mine would have to be 50 foot.

Pro bed shaper

Homemade shaper

[tapatio]

Untreated wood lasts a couple of years here.

We received a bunch of free Ipe wood and used it for raised beds. They are still in great shape after a number of years.