We do bury them so they do not bulge out from the weight of the soil. They are pressure treated lumber so they are meant from ground contact.

If the 4x4's are inside the planters instead, would we avoid the bulge but still be able to install the board on top as a bench?

Pressure treated posts contain lots of chemicals to prevent them from rotting. We recommend leaving them outside of the cedar to prevent any chemical leaching.

When you bury the posts, do you set them in concrete? Or is it enough to just have them in sunk the dirt? Also wondering if it would be safe to stain and/or paint the outer surface of the boards - that wouldn't leach into the soil where the produce is growing would it? Thanks for your help!