Mishnah 4 also deals with the acquisition of trees. The starting point is agreed upon by all: when someone buys a single tree from another, the seller remains the owner of the field, and the buyer acquires only the tree, meaning that organism above the ground (and even its roots), but not the land itself.
However, with a certain number of trees, it is obvious that the buyer acquires not only the trees but also the land connecting them, as this is not the purchase of three individual trees but the purchase of a small orchard. Hence, many practical differences depend on the question of whether the buyer is the owner of the land or not. Incidentally, our Mishnah presents a dispute among the Tannaim regarding the threshold from which it is understood that the purchase of the trees includes the purchase of the land - two or three trees.
We will follow the view of the Tanna Kamma here, according to which three trees are sold with the land, whereas one or two trees are not, and this is how the halachah is decided. But in order for the land to be acquired with the three trees, they must meet these conditions:
Maximum distance: No more than sixteen amot from each other, since trees that are too far apart do not combine.
Minimum distance: No less than four amot from each other, since trees that are too close kill each other and are not considered three separate trees.
Formation: Not in a straight line, but rather in a triangle formation.
One who buys two trees - does not acquire land:
The Mishnah establishes that one who buys two trees in another's field does not acquire the land at all. It is obvious that this is the law for one tree, and the Mishnah specifically mentions two because of the dispute among the Tannaim: Rabbi Meir holds that even with two trees, the land is acquired with them. From here emerge three laws from the Mishnah:
"Higdilu" - if the branches of the tree spread out until they cast a shadow on the crops in the landowner's field, the owner of the field is not permitted to cut them. This is because one who sells a tree without land knows that it is the nature of a tree to grow, and he must allow it to grow in its normal way.
"Veha'oleh min hageza" - branches emerging from the trunk of the tree belong to the buyer, as they are part of the tree. However, "umin hashorashim" - shoots emerging from the roots below ground are considered as growing from the land and not from the tree, and therefore they belong to the landowner.
"Ve'im metu - ein lo karka" - if the trees he bought die, the buyer takes the dead wood for firewood, but the land belongs as it was to its original owner, and the buyer is not permitted to do anything with it.
One who buys three trees - acquires land:
Once a person buys three trees that meet the listed conditions, he acquires the land with them. The assumption here is the same reservation we noted in all the Mishnayot of this chapter: we assess what a normal person meant when saying "I am buying three trees from you", and what the seller meant when saying "I am selling you three trees". In the time of the Mishnah, this included the land connecting the trees and the area around them needed for their cultivation and the gathering of their crop. Hence, the three laws are reversed:
"Higdilu - yeshapeh" - if the branches spread out and cast a shadow on the crops of the field owner, the landowner is permitted to cut them and say to the buyer: you have your own small orchard to work in, and your domain does not invade mine. The cut branches belong of course to the tree owner, but the right to cut them is given to the landowner.
"Veha'oleh min hageza umin hashorashim, shelo" - both that which emerges from the trunk and that which emerges from the roots belong to the buyer, since he is the owner of the trees and of the land beneath and around them. And even though the shoots emerge from the roots and are considered to be growing from the ground, it does not matter - the land is his, and therefore the new trees are his too.
"Ve'im metu - yesh lo karka" - if the trees die, since he is the owner of the land beneath and around them, the land remains in his possession, and he has the right to plant new trees in it.
In summary: We learned that one who buys one or two trees acquires the tree alone: the spreading of the branches cannot be prevented, he acquires what emerges from the trunk but not what emerges from the roots, and if the trees die, he has no land. In contrast, one who buys three trees standing at a distance of four to sixteen amot from each other and in a triangle formation, acquires the land with them: the field owner is permitted to cut the branches invading his area, the buyer acquires what emerges from both the trunk and the roots, and if the trees die - the land remains in his possession.