The mother tree, with Jewish roots and Gentile branches, had begun to bear fruit. How accurately this describes the early Christian era. At this time the Gentiles were blossoming in the knowledge of the resurrected Jesus Christ. One will recall that the Jewish Christians had some misgivings about taking the gospel to the Gentiles, but Paul was their champion. He understood the will of the Lord in bringing forth this great work.
’For this cause I Paul, the prisoner of Jesus Christ for you Gentiles…
That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel’ (Eph 3:1,6)
In Romans he warns the Gentiles that they must produce good fruit or they will be destroyed as the Israelites which preceded them:
’if the root be holy, so are the branches.
And if some of the branches be broken off, and thou, being a wild olive tree, were graffed in among them, and with them partakest of the root and fatness of the olive tree;
Boast not against the branches. But if thou boast, thou bearest not the root, but the root thee.
Thou wilt say then, The branches were broken off, that I might be graffed in.
Well; because of unbelief they were broken off, and thou standest by faith. Be not highminded, but fear:
For if God spared not the natural branches, take heed lest he also spare not thee…
And they also, if they abide not still in unbelief, shall be graffed in: for God is able to graff them in again. (Rom 11:16-21,23)
After Christ comes and fulfills the Law of Moses, the Gentiles are adopted into the house of Israel, as participants in a new and everlasting covenant. They, in effect, become holy branches, for the branches of the wild tree have taken hold of the moisture of the root thereof (v. 18). For the rest of the allegory, it is easier to think of the mother tree as Christianity in general, with Jewish roots and Gentile branches. In this sense, the mother tree does not have to be limited geographically to the confines of Jerusalem.