In the Bible, things that are lower down, or under, physically, generally represent things that are lower or more external spiritually. In some cases, the lower things have been separated and put away to protect the good, but in others, it can mean that a less exalted idea or good desire is supporting a more exalted one.

(Notae: Arcana Coelestia 4564 [1-2], 8610, 9656)

7689. 'And they devoured every plant in the land' means that it consumed every known fact about truth. This is clear from the meaning of 'devouring' as consuming; and from the meaning of 'a plant in the land' as a known fact about truth. For 'a plant in the field' means a truth that the Church possesses, 7571, because 'the field' is the Church, but 'a plant in the land' means a known fact about truth, because 'the land' here is the natural mind, and truth as it exists in the natural mind is factual knowledge. Furthermore the evil are not in possession of any truth of faith, only of knowledge about the truth of faith. Some evil people within the Church are convinced that they do possess the truth of faith, but they do not; they are ruled by falsity and opposed to the truth of faith. The falsity they are ruled by is deeply hidden within them as long as they are in the world, but that deeply hidden falsity emerges and reveals itself in the next life when they undergo vastation of the truths of faith they had known.