"Grass" is a symbol, a characteristic of the initial state of Man on the historical path of his spiritual "creation", formation, a symbol of his worldview and way of life before the display of the spiritual "Image" and "Likeness" of God in him.
It is also a symbol of man's initial moral, spiritual state, his practical experience, his intellectual, pragmatic knowledge.
"Grass" is also a symbol of the shortness, frailty, fragility, perishability of man's physical life.
Negative meaning.
"Grass" is a symbol, a characteristic of man, unconfirmed in the knowledge and fulfillment of the Will, of God, of His Commandments, living a creaturely, animal, purely carnal, morally and spiritually lowly life.
It is also a symbol of man's accumulated earthly, materialistic wealth, material goods used by man to please his flesh.