There are three cases of Asheirahs - a tree planted originally for idolatry is prohibited.

If he cut or trimmed a tree for idolatry (of the new sprouts) and it sprouted, he can remove the new sprouts and the rest is permitted.

If he stood an idol underneath it and then removed it, it is permitted.

(R. Ami citing R. Shimon ben Lakish): If he engraved pictures in the tree, the tree remains prohibited even if he erased them.

Beraisa: If he grafted a branch of the Asheirah onto another tree, he must merely remove the branch and the rest of the tree is permitted.

(Reish Lakish citing R. Yanai): (Qualifying the Beraisa) It must only be removed if it was grafted for the purpose of idolatry. (However, his action does not affect the rest of the tree, so if he removes that branch, the tree is permitted.)

Question: There is a contradiction in Reish Lakish - Above (d), he said that if he engraved pictures in the tree, the tree remains prohibited (which is understood to mean) even if he erased them; and here (f) he said that if a branch was grafted for the sake of idolatry, it must merely be removed and the rest of the tree is permitted?

Answer: It is a stringency in engraving, as it is considered more of a physical act done to the tree.

(R. Hila citing R. Elazar): An Asheirah is only prohibited if he put an idol under it.

Question: According to R. Elazar, there are two types of Asheirah; but the Mishnah said three?

Answer: Rather, for annulling them, there are three laws - when he planted it to serve the idol, it must be chopped down; when he chopped or trimmed a tree in order to stand an idol underneath it and it grew, he must remove the growth; and if he happened to stand an idol underneath the tree, he must merely remove the idol.

(Mishnah): What is the Asheirah (about which there is a disagreement)? Any tree that has an idol underneath it.

(R. Shimon): Only if it is worshipped.

There was a story in Tzidan of a tree that they were worshiping and under it was a pile of stones.

R. Shimon told them to examine the pile. They examined it and found an image on it. R. Shimon said, "Since they were worshiping the image, we can permit for them the tree itself."

(Gemara) (Rav Chisda): The Tannaim disagree of a case when it is uncertain...if it is certain that they serve the image and the tree, all agree that the tree is prohibited; if it is certain that they serve the image but not the tree, all agree that the tree is permitted...

Rather, they disagree when it is uncertain what they serve - R. Shimon said that they can be assumed to serve the image but not the tree; Rabbanan say that they can be assumed to serve the image and the tree. (Note: Several Rishonim adjust the text in this way.)

Question: Would R. Shimon disagree with the Rabbis (who are the majority opinion) and then even make a ruling against them (in the Mishnah in the case that occurred in Tzidan, above (c))? (This question remains unanswered.)

(Mishnah): One may not sit in its shade, but if he did, he remains Tahor. He may not pass underneath it, and if he did, he becomes Tamei.

If it hangs over a public path and he passed underneath it, he remains Tahor.

One may plant underneath it in the rainy season (as its shade does not benefit the seeds) but not in the summer. Lettuce may not be planted even in the rainy season.

(R. Yosi): Vegetables may also not be planted in the rainy season because the tree's leaves fall upon them and fertilize them.

(Gemara) (In Bavel in the name of Rav Chisda): Its shade is prohibited; the shade of its shade is permitted. What is that? In Bavel they say - in the morning or evening, the shade of the tree is very long. Any shade that is less than the height of the tree is called its shade (and is more intense); any shade that continues beyond the height of the tree is weaker and is called 'the shade of its shade'.

Question: Why is its shade prohibited?

Answer: If it is because one gains benefit from it, but one may sit in the shade of a grave, even though it is also prohibited to gain benefit from it? And also, one may not gain benefit from the Heichal, but R. Yochanan ben Zakai would sit and teach in its shade? Rather, the reason is not because one may not gain benefit from it.

Conclusion of answer: Rather, it is a Rabbinic stringency applied to idolatry.