'Olive tree' in the Bible

Now if some of the branches were broken off, and you, though a wild olive branch, were grafted in among them and have come to share in the rich root of the cultivated olive tree,

And these Jews also will be grafted [back] in [to the olive tree] if they do not continue in their lack of faith [in Christ], because God is able to graft them back in again.

For, if, thou, out of the naturally wild olive was cut out, and, beyond nature, hast been engrafted into the good olive, how much rather, shall these, the natural branches be engrafted into their own olive tree?