A spirit living in a tree is read as the life force of nature itself, and of growth that takes its time. Folk belief treats it as a guardian, so meeting one is often read as being asked to respect something slow and old.
Has this come up in your dreams before? What was going on in your life then?
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.