In Norse myth the world tree was an ash, linking the heavens, the earth and the underworld. Dreaming of one is read as connection, growth and a broader view of your place in things.
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.