Israel is a luxuriant vine that puts forth his fruit. According to the abundance of his fruit he has multiplied his altars. As their land has prospered, they have adorned their sacred stones.
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.