Free retaining walls

My garden is on a slope that had no topsoil to speak of, so I wanted to build raised beds. Since I cut down some trees to let light into the garden, I had plenty of free material on hand.

After I dropped a tree, I cut its trunk into angled sections. Then I stood the sections on the slope, with the angled bottom placed so the wood leaned uphill a bit.

After building a bed, I lined the back walls with black plastic and poked a few drainage holes. There's no plastic in the bottoms of the beds. Then I filled each bed with topsoil from a pile dumped regrettably far uphill.

I also cut slots in trunk sections and fit scavenged sawmill siding into the slots. I like this look better than the wall of trunks.

It's been five years and the wood is definitely rotting, especially the smaller pieces. But no beds are in danger of trickling downhill yet. I plan to slowly replace the wood with limestone spalls from a local quarry.