Reference for Bava Batra 5:4
הַקּוֹנֶה שְׁנֵי אִילָנוֹת בְּתוֹךְ שְׂדֵה חֲבֵרוֹ, הֲרֵי זֶה לֹא קָנָה קַרְקַע. רַבִּי מֵאִיר אוֹמֵר, קָנָה קַרְקַע. הִגְדִּילוּ, לֹא יְשַׁפֶּה. וְהָעוֹלֶה מִן הַגֶּזַע, שֶׁלּוֹ. וּמִן הַשָּׁרָשִׁים, שֶׁל בַּעַל הַקַּרְקַע. וְאִם מֵתוּ, אֵין לוֹ קַרְקַע. קָנָה שְׁלֹשָׁה, קָנָה קַרְקַע. הִגְדִּילוּ, יְשַׁפֶּה. וְהָעוֹלֶה מִן הַגֶּזַע וּמִן הַשָּׁרָשִׁין, שֶׁלּוֹ. וְאִם מֵתוּ, יֶשׁ לוֹ קַרְקַע:
One who buys "two trees" [unqualified] in the midst of his neighbor's field does not acquire [any] land [around them.] R. Meir says: He does acquire land. If they grew, he [the owner of the land] may not cut them, [even though their shade harms his land. For since the owner of the trees has no land, (it is understood that) the owner of the field has "bound" his land to him for all of their requirements so long as they are there.] And what grows from the trunk [i.e., whatever is above the ground, "beholding" the sun] is his [the tree owner's. Not that he should let it grow there; for we fear that the soil might rise until part of the tree growing out of the trunk is covered with it, so that the impression is given of three trees and the buyer might say to him: "You sold me three trees and I own (their) land." (see below) But he must cut it and burn it.] And (what grows) from the roots [i.e., whatever is below the ground] is the land owner's. And if they died [i.e., if the trees dried up], he (the tree owner) has no land [on which to plant others in their place.] If he bought three (trees), he acquires the land, [it being considered a "tree-field," and he acquires the land between tree and tree, and beneath them, and to the side, the full (space) of a fruit picker and his basket, so that he can stand there with his basket and pick. This, when there is no less between tree and tree than four cubits and no more than sixteen. It is only then that he acquires the land as indicated. But if there is less between tree and tree than four cubits or more than sixteen, he does not acquire the land.] If they grew, he (the field owner) may cut them. And what grows from the trunk and from the roots is his (the tree owner's). And if they died, he (the tree owner) has land (on which to re-plant them).