1,156. Grafting

174:1 Diverse species of trees are included in the prohibition of Leviticus 19:19, "Do not sow your field with different species."  It is therefore prohibited to graft a tree of one species onto a tree of a different species, such as the branch of an apple tree onto an esrog tree or vice versa. This is the case even when the species are similar,  such as the branch of an apple tree onto a crab apple tree. Since they are two different species, it is forbidden to graft them together. It is likewise forbidden for a Jew to have a non-Jew graft different trees for him.

174:2 We are not permitted to keep a tree that was grafted with a different type of tree but the fruit that grew from it is permitted. It is permitted to take a branch from a grafted tree and to transplant it elsewhere.