What is "k'Ar'ar"?
Rashi #1: It is a lone tree. It is an expression of Ariri (Bereishis 15:2, childless).
Rashi #2: Some say that it is destroyed and ruined.
Rashi citing Menachem: It is the name of a forest tree. So he explained "k'Aro'er ba'Midbar" (48:6).
Targum Yonasan: K'Akovisa. Radak citing Rav Hai Gaon - there is a thorn outside, and edible fruit inside 1 .
Malbim: It is Ariri - it does not receive any influence from Shamayim.
Perhaps it is sabra. (PF)
What is "Aravah"?
Rashi: It is a plain.
Why does it say "v'Lo Yir'eh"?
Radak: This is an anthropomorphism. Malbim - also from its surroundings and neighbor it gets no benefit, for it is among thorns and dry [trees].
What does "Tov" refer to?
Radak: It is rain.
What is the meaning of "Charerim"?
Rashi: It is dry, like "Charah Mini Chorev" (Iyov 30:30).
Radak: It is burning heat; this is why rain does not fall in the Midbar. This is like "v'Atzmi Charah Mini Chorev"(Iyov 30:30), "v'Charah Nechushtah" (Yechezkel 24:11), "Nachar Mapu'ach" (above, 6:29). Charerim is a noun, like Metzarim (distresses). The matter is repeated in different words.
Why does it say "Eretz Melechah"?
Radak: Melechah is an adjective, for a land that does not sprout; it is cut off from settlement. Also "Bris Melach" (Bereishis 18:19) is a Bris that is cut, and "Eretz Pri li'Melechah" (Tehilim 107:34).
Radak citing Targum Yonasan: Like the land of Sedom, which was inhabited (after its destruction).
Malbim: Also from its roots, the tree does not get [water].
What is the meaning of "v'Lo Seshev"?
Rashi: It will not be inhabited (because the land is salty).
Radak: One who removes his trust from Hashem is compared to this tree, which is not moist. It is always dry; even so, it does not die. So this man will have evil all his days; he will prefer death to life.