Midrash su Levitico 19:23

1) (Vayikra 19:23) ("And when you come to the land and you plant every food tree, then you shall count as forbidden its fruit. Three years it shall be to you forbidden; it shall not be eaten.") "when you come": I might think (that the laws of arlah apply) when they come to trans-Jordan; it is, therefore, written: "to the land" — to the specific land (i.e., Eretz Yisrael proper).

(Exodus 12:2) "The beginning of the months": We are hereby apprised that Nissan is the beginning for the months. And whence do we derive (the same for) the reign of kings? From (I Kings 6:1) "In the fourth year of Solomon's reign over Israel, in the month of Ziv (Iyyar), the second month," (his reign having begun with the first month, Nissan). And whence do we derive (the same for) festivals (i.e., that one is not in transgression of delaying his vows until three consecutive festivals have passed)? From (Devarim 16:16) "… the festival of matzoth (in Nissan), and the festival of Shavuoth, and the festival of Succoth." We find, then, that Nissan is the beginning for months, for kings, and for festivals. R. Nathan and R. Tzaddok say: Also for house rentals (i.e., If one says: I am renting it to you for this year, the understanding is until the beginning of Nissan.) But this does not apply to (the reckoning of) years, shemitah, Yovloth, planting (in respect to arlah [viz. Leviticus 19:23]) or (the tithing of) greens, in which respect it is written (Devarim 31:10-11) "At the end of seven years, in the time of the year of the shemitah … when all of Israel, etc.", and (Exodus 34:22) "and the festival of the ingathering, the circuit of the year."

2) "when you come … and you plant": to exclude (from arlah) what was planted by the gentiles before they entered the land. — But perhaps I exclude what was planted by gentiles after they came to the land! It is, therefore, written "every tree" — whence they ruled: What our ancestors found to have been planted before they came to the land is exempt (from arlah). What they planted, even before they had conquered the land, is subject (to arlah). "and you plant": to exclude what grows of itself. "and you plant": to exclude (from arlah) what is engrafted and what is sunk (in the ground to grow as an independent plant) — whence they ruled: The connection of grape vines and the engrafting on an engrafted part, even though it is sunk into the ground, is permitted (vis-à-vis arlah). R. Meir says: If (he sunk into the ground) a healthy (self-sufficient) engrafting, it is permitted; if, an unhealthy engrafting, it is forbidden. This tells me (as being subject to arlah) only of his planting a nut and an almond. Whence do I derive the same for planting a young shoot (thereof)? From "tree" (including a shoot thereof). "food tree": and not a barren tree. "food tree": to exclude what is planted for fencing, beams, and fuel. R. Yossi says: Even if he said: The inner is for food and the outer for fencing, the inner is subject (to arlah), and the outer not.