This poem is called "Grass," and it's spoken by that very same green grass. For more on the type of speaker this grass makes, head on over to our "Speaker" section.
But don't leave just yet. If you're an avid poetry reader, this title just might make your heart flutter, 'cause it just might remind you of Walt Whitman's Leaves of Grass, which is pretty much the most famous (and, in our humble opinion, the most important) book of nineteenth-century American poetry.
Whitman's poem, "Song of Myself," features a lengthy meditation on the nature and different uses of, that's right, you guessed it, grass. For Whitman, grass is "the handkerchief of the Lord," "the babe of vegetation," even "the beautiful uncut hair of graves." For Whitman, grass is a symbol of faith, love, new life, but also of death. (If you want to know more about Whitman, head on over here.)
It's this life-death symbolic combo that interests Sandburg in his poem "Grass." The title, then, tells us both what the subject of the poem is going to be, as well as who the speaker of this poem is going to be. It does a lot of summarizing for just one word, but then again, grass in this poem is all about getting down to work.