Symbolism, Imagery, Allegory
Isaiah constantly compares human beings to vegetation—growing, flourishing and dying. And aside from vineyards, grass is one of the central examples. Isaiah 40:6-7 reads,
All flesh is grass, and all the goodliness thereof is as the flower of the field: The grass withereth, the flower fadeth: because the spirit of the Lord bloweth upon it: surely the people is grass.
It's sort of a melancholy image—the grass has its day to live, but when God blows his breath on it, it dries up.
This image has been really influential—Walt Whitman uses it in his masterpiece, Leaves of Grass, constantly meditating on the meaning of the smallest blade of grass, and trying to find hope for immortality and the continuation of life. Even though people and grass both die, the grass hints that there's a future rebirth or renewal to come, since it sprouts up from the decaying matter left by everything that dies. Life leads on to death and death leads on to life.