3,028. Grafting Trees

Hilchos Kilayim 1:4

The prohibition of mixed species only applies to plants that are suitable for human consumption. Bitter grasses and similar roots that are only suitable for medical purposes and other such plants are not prohibited because of kilayim.

Hilchos Kilayim 1:5

Trees are included in the prohibition against planting one’s field with mixed species (Lev. 19:19). Accordingly, if someone grafts one type of tree onto a different type of tree – like an apple branch onto an esrog tree or an esrog branch onto an apple tree – then he is liable to lashes under Biblical law both in Israel and elsewhere. Similarly, if one grafts a vegetable to a tree or vice versa, he is liable to lashes in any location.