I wanted to use cedar for the smell but it seems the oils in cedar prevent moss growth. Pine does double duty in weed prevention and raising acidity. You could use sphagnum moss but that might end up encouraging mold.

Of course one could trest it like a terrarium/paludarium and put springtails in your greenhouse.

Uh-oh. I might have just added a lot more work to my plate. We were already planning on a container pond but maybe now we’ll make it a full on mini-ecosystem in there.