"The human being is a tree of the field". (Deuteronomy 20:19)

Interestingly, the Jewish calendar reserves one day each year, the "New Year for Trees" on the 15th of Shevat, for us to contemplate our affinity with the botanical universe.

Why is the human being compared, in the biblical imagination, to a tree?

Roots, Body & Fruit

A tree’s primary components are: the roots, which anchor it to the ground and supply it with water and other nutrients; the trunk, branches and leaves that comprise its body; and the fruit, which is harvested and enjoyed by humans or animals and also contains the seeds through which the tree reproduces itself.

...a human being is also comprised of three components: roots, a body, and fruit.

This is why the Torah compares us to trees, because a human being is also comprised of three components: roots, a body, and fruit. This comparison holds true on three levels: psychologically, chronologically and spiritually.

The roots of the tree, buried underground and mostly invisible, represent the subconscious layers of the human psyche, which are for the most part invisible. Just like the roots of a tree, the composition, breadth and depth of the human subconscious are disguised and constitute the roots of all manifestations of the human self.

The body of the tree – the conspicuous manifestation of its roots — symbolizes the conscious personality of the human being, the way we describe our existence consciously to ourselves. It is the "person" you (think you) know.

The fruit of the tree – harvested and consumed by others – represent the impact we have on the lives of people around us; it embodies our ability to plant a seed in a fellow human being and see it sprout, grow and bear fruit.

Childhood, Adulthood & Leadership

On a chronological level, the roots represent the childhood years, when our subconscious convictions and feelings are being molded, which is why investing time and energy in children is the most noble and critical endeavor. A scratch on the trunk does not amount to much; a defect in the roots can impact the entire tree in dramatic ways. The significance of childhood is often invisible like roots of a tree, but it is the foundation of everything that comes later. Nurture those roots and your tree will be beautiful.

As we graduate childhood and become self-efficient humans, we are compared to the tall and projective trunk of the tree. At last we have emerged to become independent and self-standing adults.

Then, as we grow older and become leaders in our communities, as we marry, bear children and create something larger than ourselves, we begin to produce "fruit" that continue to procreate and impact generations to come.

Conviction, Study & Giving

...the roots represent faith, our source of nurture and perseverance.

On a spiritual level, the roots represent faith, our source of nurture and perseverance. The trunk is the visible "body" of our spiritual lives — our intellectual, emotional and practical achievements; our study of Torah, observance of mitzvos and daily ethical activities. Finally, the fruit represents our power of spiritual procreation — the ability to influence others, to plant our seeds in their souls.

Faith, just like roots, constitutes the foundation of life (without roots, a tree cannot survive). Our belief in the essential spirituality and meaning of life is the foundation of our entire "tree." From it stems the trunk of our understanding, from which branch out our feelings, motivations and deeds. Yet the true extent of faith is concealed from others and even from ourselves. For while the body of the tree also provides nurture (via its leaves) – representing the nurture that comes from Torah and Mitzvos — the bulk of our spiritual sustenance derives from its roots, from our conviction that life has meaning and that there is somebody at the core of reality that cares.

"The human being is a tree of the field." We operate on three levels. There is who we are (the roots); who we think we are (the trunk), and who others think we are (the fruit). In a tree, the three components are integrated into a single, wholesome entity. Our job, the Torah is intimating, is to integrate the components of our "tree," so that our roots, bodies and fruits become one.

[From //algemeiner.com, where the author cites that part of this article is based on a letter by the Lubavitcher Rebbe dated Shevat 21, 5704 (February 15, 1944), published in Igros Kodesh vol. 1 pp. 247-250.]