We use rough cut cedar and line the inside with pond liner for protection from the soil. We also like to stain the outside so they last longer.

Hi - I really like this design and plan to build in my yard. When you line the inside, are you stapling a liner to the wood and leaving the bottom open? Is the 2x10 lumber setting on the gravel or dirt? Is there gravel under the dirt? Did you put newspaper at the bottom or screen?