Shiitake grows on fallen logs, and dream books read it as something rich and nourishing that rises out of what has ended or decayed.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.