Garden Terrace Wall with Wood 1

In this project I was building small retaining walls for a three tiered side-yard garden. It was simple enough just to drill holes through 4x4s and hammer re-bar through them into the ground. It was small enough for me to join the edges with ornate peaked fence posts. I'm against used "treated" wood in the garden so I tried a natural sealant, it won't last forever, but nothing does anyway and I'd rather less than more toxic chemicals in the garden.