Tree from the Garden of Earthly Delights, left panel
The question of how material reality is related to the higher level of the spiritual begins, in some senses, with this idea of the soul as a tree.
In order to understand this we first need to understand that everything material is a reflection of the spiritual; and everything material functions by way of analogy, or what Swedenborg would have called correspondences. That is why all of nature replicates itself, from top to bottom, with material phenomena that mirror one another in both structure and purpose.
Let us recall that plants are the fundamental building blocks or organic life; all animal life depends on plant life to make its food for it. In the same exact way, all of material reality is in a certain sense a vegetative entity, that is, material reality serves as a receiving organism for the emanations of the divine, whereby it receives them and converts them into food for the spiritual level.
The old adage that man is "food for Angels" follows this idea in general, although it doesn't explain it with the precision it ought to. The leaves on the tree of the soul are infused with an active substance akin to the chlorophyll of plants; and it's only through this substance that the energy of the spiritual can be converted to the "inner sugars" so necessary for the maintenance of the spiritual world. The reason that spiritual rewards are so often described by the masters as "sweetness" is precisely because of this correspondence between the sugars created in photosynthesis and the sugars created by the action of Being. They are not different, except by level; and so in the same way that sugars created by plants are sweet, so are the sugars of the soul equally sweet. We call this the "sweetness of the Lord," without correctly understanding the correspondences involved. Yet when we experience this sweetness, it is a true sweetness exactly like that of the taste of sugar, yet received in the soul, not on the tongue—and magnified a thousandfold. Equally, it may be a perfume—or musk, as Rumi called it—equally sweet, and equally real, yet sublime and impossible to explain.
It's no coincidence, in other words, that Christ used parables referring to the growth of plants in explaining the development of the soul. They are more than just analogies; there is a science to it conforming to laws we are already familiar with, governed by the biology of our own level, but subservient to a much larger truth of which they are a single fractal.