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.

“The eyes are the windows of the soul.” That's a sentiment with roots somewhere in murky antiquity, but one that has become hopelessly cliché because it is both poetic and obviously true. We feel that if we can look in someone's eyes, we can truly know what they are inside. And it's not just the eyes; really it is the face as a whole that conveys this. As Swedenborg puts it, the face is “man's spiritual world presented in his natural world” (Heaven and Hell, No. 91). Our faces reveal our interior thoughts and feelings in myriad ways, which is why psychologists, poker players and criminal investigators spend so much time studying them. It makes sense, then, that people's faces in the Bible represent their interiors, the thoughts, loves and desires they hold most deeply. We turn our faces to the ground to show humility when we bow in worship; we turn them to the mountains when seeking inspiration; we turn them toward our enemies when we are ready to battle temptation. When things are hard, we need to “face facts,” or accept them internally. When the topic is the Lord's face, it represents the Lord's interiors, which are perfect love and perfect mercy. And when people turn away from the Lord and refuse his love, it is described as the Lord “hiding his face.”

(References: Heaven and Hell 91)