Are trees grown indoors, in unperforated pots, subject to orlah laws?

Answer

Note: definitions and laws pertaining to indoor plants and unperforated pots often differ vis-à-vis orlah, terumot and ma'aserot, shemitah, and kilayim.

Orlah and unperforated pots

The Yerushalmi (Orlah 1:2) states: "A tree planted in an unperforated pot is subject to orlah." Rabbi Yose explains that this is because the roots penetrate through the pot and receive nourishment this way. Rambam (Hilchot Ma'aser Sheni 10:8) explains: "A tree planted in an unperforated pot is subject to orlah; while the pot is not 'land' for seeds, it is considered 'land' for trees." The Shulchan Aruch rules likewise (YD, §294:26).

Posekim deliberate regarding metal pots (since unperforated pots were generally made of pottery, which is more porous than metal), which serve as a complete barrier between the pot and the ground; perhaps according to the Yerushalmi's reasoning these would be exempt from orlah (this is not brought down as halachah, though). While some posekim hold that unperforated pots are subject to orlah mide'oraita, others maintain that they are completely exempt. The accepted ruling is that such trees are subject to orlah miderabanan.

Orlah indoors

The Yerushalmi states (ibid) : "A tree planted in the house is subject to orlah." The Rambam (ibid., 10:9) rules accordingly. The Penei Moshe explains that in reference to orlah, the Torah does not write sadeh, field; rather aretz, land ("When you come to the land and you plant trees," Vayikra 19:23); so planting indoors also qualifies as "in the land."

Orlah indoors in unperforated pots

Trees growing indoors in unperforated pots are subject to orlah miderabanan (they are considered disconnected from the ground; here the barrier is twofold: the tree is in a pot, and there are tiles on the floor).