I don't know where you get this? A tree is established in a plot of ground. That's likely Israel after she was established as a nation in the land of Israel. The "roots," then, would be Abrahamic faith, or the faith of the Patriarchs.
Gentile converts to Christianity were branches added to the tree as long as Israel continued as a nation, because there was no other tree. But later, Gentile Christianity developed their own "trees," when entire nations converted to the faith.
The "roots" still belonged, perhaps to Abraham, but the Christian nations have appropriated Abraham's roots for their own "trees."
Dialogue between Jews and JESUS: John 8KJV
Jews said: - We be Abraham's seed,...John 8:v.33KJV
- JESUS said: - I know that ye are Abraham's seed...John 8:v.37KJV (Positive)
Jews said: - Abraham is our father.... John 8:v.39KJV
- JESUS said:- If ye were Abraham's children...John 8:v.39KJV (If???? hum!!!)
Jews said: - We be not born of fornication; we have one Father, even God. John 8:v.41KJV
- JESUS said: - If GOD were your Father...John 8:v.42KJV (If???? hum!!!)
- JESUS said to the Jews: Why do ye not understand my speech? John 8:v.43
- JESUS openly and emphaticaly said to the Jews: Ye are of your father the Devil..., John 8:v.44 - (Should we believe in JESUS here?)
In Revelation 12:v. 9KJV, JESUS said: And the great Dragon (the red Dragon) was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his messengers were cast out with him. By the way, "red Dragon" is the new name of the Devil in this time of Apocalypse)
Genesis 3:v.4-7KJV
4 And the serpent said unto the woman, Ye shall not surely die:
6 And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat.
7 And the eyes of them both were opened, and they knew that they were naked;
And they sewed fig leaves together, and made themselves aprons. (Fig leaves? Yeah, fig leaves, course, even in the Garden of GOD, in Eden)
Even JESUS said to the Jews: Ye are of your father the Devil...,
Why did JESUS call the Jews of serpents? It is because they are sons of the old serpent, called the Devil and Satan, now red Dragon.
Matt.23:v.33-35: 33 -Ye serpents, ye generation of vipers, how can ye escape the damnation of hell?
34 Wherefore, behold, I send unto you prophets, and wise men, and scribes: and some of them ye shall kill and crucify; and some of them shall ye scourge in your synagogues, and persecute them from city to city:
35 That upon you may come all the righteous blood shed upon the earth, from the blood of righteous Abel unto the blood of Zacharias son of Barachias, whom ye slew between the temple and the altar.
What is the MYSTERY of JESUS had linked the Jews to the murder of Abel? Who killed Abel? That upon the Jews may come all the righteous blood shed upon the earth beginning by te blood of Abel? GOD caused the NATION of Israel, the clay, the dry land, to spring up out of the earth in the middle of the third Day. The NATION of Israel was created around 2.500 years after Adam or 1.500 years B.C., so Israel appeared in the half of the third Day of GODs' works.
For we must all appear before the Judgment seat of Christ; that every one may receive the things done in his body, according to that he hath done, whether it be good or bad. 2 Corinthians 5:v.10