Several years ago in Kyoto I bought a small fern in what looks like a charcoalized tree trunk, about 3 inches high x 3 inches across. Like the moss balls with bonsai-ed trees, shrubs, etc. these had to be watered daily and there was a wide variety of plants offered including small Japanese maples. The top is hollowed out to accept the plant. I have planted my own plugs in it over the years with varying success (appropriate plugs difficult to get locally). I am really curious to know what the container is made of. It's obviously organic, but the bottom cross section does not look like a tree. I wondered if it might be some kind of gourd like vegetable.