In Exodus 34:13, Deuteronomy 7:5, Deuteronomy 12:3, God states laws against idolatry, and God says to cut down or burn groves:
Exodus 34:13 KJV
But ye shall destroy their altars, break their images, and cut down their groves:
Deuteronomy 7:5 KJV
But thus shall ye deal with them; ye shall destroy their altars, and break down their images, and cut down their groves, and burn their graven images with fire.
Deuteronomy 12:3 KJV
And ye shall overthrow their altars, and break their pillars, and burn their groves with fire; and ye shall hew down the graven images of their gods, and destroy the names of them out of that place.
Some kings, fighting against idolatry, accomplished that commandment, like Hezekiah :
2 Kings 18:4 KJV
He removed the high places, and brake the images, and cut down the groves, and brake in pieces the brasen serpent that Moses had made: for unto those days the children of Israel did burn incense to it: and he called it Nehushtan.
In my native language (portuguese), "grove" is translated as a "forest". So I thought: What's the problem with some trees? What's related to idolatry on groves?
Using strong, the "grove" word is H842 (happy; asherah (or Astarte) a Phoenician goddess; also an image of the same). God was fighting the idolatry about that goddess?