There were various trees in the Garden of Eden, we are not all of the same kinds of trees -Oaks, Cedars, Pine, Dogwood, Crape Myrtle-, whether fruit trees we all have attributes that make up the children of God. Tree here is used as a Simile. So we have to see that God is the Husbandman and that we abide in Him or are cast away and are burned by men, any tree that the Father had not planted will be hewn down at the root of the tree.