The high places also of Aven, the sin of Israel, will be destroyed. The thorn and the thistle will come up on their altars. They will tell the mountains, "Cover us!" and the hills, "Fall on us!"
So, because they had broken the covenant with God, they were swearing falsely when they made that covenant with God, thus God's judgment is gonna spring up upon them, just like weeds, the poison weed of hemlock just grows up in the fields.