Bava Batra 27 - First-Fruit Must be From Your Land
Ulla said: "A tree that is within sixteen amot (~30 feet) of a boundary is a 'thief,' because it draws nutrients illegally from a neighboring field." One does not bring first-fruit from it - because it should be "... from your field ..." and because stolen produce in unfit for Temple service.
Question against Ulla: Rabbi Akiva said, "Even a minute measure of land is subject to the requirements of first-fruit , and it is fit to write prosbul on its account .
Ulla answers: "Rabbi Akiva is talking about wheat, not a tree." Only wheat can grow on a minute measure of land.
However, one of Yehoshua's conditions when dividing Israel was that the practice of planting trees near the border should be tolerated by neighbors, thus making the first-fruit fit.