To establish man's faith in Islam, man's first mission is to plan a tree and set the root or foundation so strong that any obstacle that may set forth, he will still stand and be strong. Here, the root of tree may refer to man's aqidah and man's knowledge in life. These is the main foundation to set man to a true and guided path where God has already laid them.
In general, as you probably already know, Iman is referred to as a root of tree and Islam as its trunk/branches while akhlaq referred to the fruits/flower. Same goes to parable which Muslim can be preferred to as a tree, the tree of Islam.
Ibn 'Umar reported: "The Prophet pbuh said: