In general, trees represent the deepest and most significant intellectual concepts: the ones that come to us most directly from the Lord. This varies depending on us and our states: the people of the Most Ancient Church, who were in a state of loving the Lord, understood truth automatically and internally through what the Writings call "perception"; people in lower states (including most of us) have to work a little harder to learn it from the Word and by willing to follow the Lord. In other parts of the Bible, especially in the prophets and New Testament parables, the meaning of "tree" is broader, meaning not just a person's intellectual concepts but the whole person.

'Trees,' as in Joel 1:10-12, signify knowledges.

1695. That 'all their food' means the power to think what was false is clear from the meaning of 'food'. What the celestial, spiritual, and natural food are which people enjoy in the next life has been shown already in 56, 58, 680, 681. These also correspond to food for the body, and therefore they are also represented in the Word by food and are actually called food. The food of evil and hellish spirits however is that which is the reverse of wisdom, intelligence, and true knowledge, namely all falsity; and what is remarkable, evil spirits are also sustained by this food. The reason they are sustained by it is that it is their life. Unless they are given the opportunity to revile the truth, and indeed to blaspheme it, they cannot live. Yet they are not given the freedom to think and speak anything false except that which subsists from their own evil; they are not free to think or speak that which is contrary to their own evil, for this is deception. Insofar as their own evil is the origin of the falsity they express, their own life is the source of it; and in this case it is also forgiven them, since their nature is such that they could not otherwise live at all.

[2] With regard to their being stripped of the power to do evil and to think falsity, the situation is that in the conflicts brought about by temptations evil spirits are permitted to draw forth all the evil and falsity residing in a person, and to fight from that person's evil and falsity. But once they have been overcome they are no longer allowed to do so, for, being within that person, they instantly perceive that good and truth have been confirmed. Such perception exists more completely with spirits than with men. From the very sphere of a person confirmed in truth and good they recognize in an instant what the situation is, what response they will get, and much else. This is quite clear in the case of a spiritual and regenerate person, with whom evil spirits are present just as much as they are with one who is not regenerate; but with the regenerate person they have been subdued and are subservient. These are the things meant by their being stripped of the power to do evil and to think falsity.