What is The Grass?

A child said What is the grass? fetching it to me with full hands;
How could I answer the child? I do not know what it is any more than he.
I guess it must be the flag of my disposition, out of hopeful green stuff woven.
Or I guess if is the handkerchief of the Lord,
A scented gift and remembrancer designedly dropt,
Bearing the owner’s name someway in the corners, that we
may see and remark, and say Whose?