[If] someone plants two rows [of vines] — if there are not eight cubits between them, he may not bring [foreign] seed there. [If] there were three [rows] — if there are not sixteen cubits between one row and the next, he may not bring [foreign] seed there. R’ Eliezer ben Yaakov says in the name of Chanina ben Chachinai: Even if the middle [row] is destroyed, and there are not sixteen cubits between one row and the next, he may not bring seed there, even though had they been planted [thus] to begin with, it would have been permitted with eight cubits.