I use sphagnum moss and collected moss sieved and mixed 50/50 and sprinkled on the surface of the pot. This helps to keep moisture in. If I am showing the tree then I add moss to the pot, I may or may not remove it after showing.
Thanks Geoff. So any moss collected outside if fine?
Yes, I collect from anywhere I can find it, outside my gate I found loads and just took a scraper and took as little soil as possible and it works fine.