Never heard of using buttermilk for anything in the garden, Kate. But if your piece of palm wood already has moss going on it, it will spread of its own accord if the base you put it on is compatible. Try taking a piece and putting it on another mount?
I'd definitely try sticking an orchid on that piece of wood. Phals grow on palm trees in nature, I believe, with their roots upwards attached to the tree and leaves pointing down, then the flowers cascade beautifully when they bloom. (not like you buy in the store, upside down with the flowers staked upwards).
