In the first line of Walt Whitman's Song of Myself, a child asks the poet to define it:  
A Carl Sandburg poem with this title invokes the battles of Austerlitz, Waterloo, Gettysburg, Ypres and Verdun, suggesting that "two years, ten years, and the passengers ask the conductor:  What place is this?  Where are we now?"  In the first line of Walt Whitman's Song of Myself, a child asks the poet to define it:  "I guess it must be the flag of my disposition, out of hopeful green stuff woven."  For 10 points, name this natural floral phenomenon.
A Carl Sandburg poem with this title invokes the battles of Austerlitz, Waterloo, Gettysburg, Ypres and Verdun, suggesting that "two years, ten years, and the passengers ask the conductor:  
Grass  (Sandburg's poem Grass; "What is the grass?")