What does the Radley tree symbolize in the novel To Kill a Mockingbird by Harper Lee?

Throughout the novel, the reclusive Boo Radley gives Jem and Scout small gifts via the knothole in the oak tree which is located in his yard. The oak tree could symbolize friendship, compassion, and communication. Boo uses the oak tree as a means to communicate with the outside world and demonstrates his compassion for the children by giving them gifts in the knothole of the tree. Boo Radley's gifts are tokens of his friendship, and the tree symbolizes his affection for Jem and Scout. Unfortunately, Boo's brother, Nathan, fills the knothole in with cement and lies to Jem by telling him that the tree is dying. Nathan does not want Boo communicating with the children, which is why he chose to close the hole. Filling the knothole with cement ends their communication and impedes their indirect friendship. For this reason, the tree can also symbolize the cruel nature of the Radley family and the negative effects of psychological abuse.