Fruit growing on branches that belong to Shimon but the trunk belongs to Reuven
Question
There is a tree whose trunk is primarily located in Reuven’s garden, while its canopy extends into Shimon’s garden. Reuven transferred ownership of the canopy to Shimon. The question is: Are the fruits that grow on the canopy—which now belong to Shimon—obligated in terumot and ma'aserot mide’oraita?
Or, since the trunk is rooted in Reuven’s property, does this constitute a deficiency in the criterion of "זרעך פרט ללקוח" —excluding acquired produce—thus rendering the obligation only derabanan? This follows the view of certain Rishonim who hold that even if the final processing (gemar melachah) is performed by the buyer, there is no Torah-level obligation.
The practical implication would be whether one may separate tithes from these fruits on behalf of fruits from a tree that grows entirely in Shimon’s garden—assuming the level of obligation must be the same.
Answer
Short Answer:
Practically speaking, the fruits growing on the branches that belong to Shimon are not considered "purchased" ("lekuchot"), because these fruits are entirely his from the moment they begin to form—since the branches themselves are fully his, having been given to him as a gift from Reuven.
Even though the branches draw nourishment from Reuven’s trunk, there is no exemption of lekuchot due to such nourishment—just as there is no lekuchot status for a tree drawing nourishment from soil owned by someone else.
Therefore, the obligation to separate terumot u’maasrot from these fruits is of the same level as the obligation on fruits grown in Shimon’s own garden. Consequently, according to all opinions, he may separate terumot u’maasrot from these fruits on behalf of other fruits growing in his garden.
Expanded Explanation:
Indeed, there is a discussion among the posekim regarding the separation of terumot and ma'aserot from fruits grown on a jointly owned tree—whether the partners may tithe after dividing the fruits. This discussion leads into the opinion that “ein bereira” (retroactive clarification is not valid), which implies that each partner retains partial ownership in every single fruit. Accordingly, each one effectively transfers his share in the fruits to the other, creating a situation where some fruits are considered lekuchot (acquired), possibly triggering a different level of obligation—especially according to those posekim who hold that even if the final processing (gemar melachah) was done by the acquirer, there is still a rabbinic exemption for lekuchot.
However, your case is not comparable. In your scenario, the fruits growing on the branches that are owned by Shimon are not lekuchot, because they are fully his from the outset—since the branches themselves were fully transferred to his ownership as a gift from Reuven. While it is true that the branches draw sustenance from Reuven’s trunk, this does not create a lekuchot exemption, just as a tree nourished by soil owned by another person is not considered lakuach.
Therefore, the level of obligation to separate terumot and ma'aserot from these fruits is the same as that of fruits growing in Shimon’s own garden. Consequently, he may, according to all opinions, separate terumot and ma'aserot from these fruits for other fruits in his garden.