Walt Whitman - Poetry

Walt Whitman is one of the biggest names in American poetry and I know next to nothing of his work.  This snippet is from 'Song of Myself', though I don't know if it's the first part or something in the middle.  I've heard of 'Leaves of Grass'.  Maybe this is from there.

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 it is the handkerchief of the Lord,
A scented gift and remembrancer designedly dropt,
Bear the owner's name someway in the corners, that we may see and remark, and say Whose?

Or I guess the grass is itself a child, the produced babe of the vegetation.

Or I guess it is a uniform hieroglypic,
And it means, Sprouting alike in broad zones and narrow zones,
Growing among black folks as among white,
Kanuck, Tuckahoe, Congressman, Cuff, I give them the same, I receive them the same.

And now it seems to me the beautiful uncut hair of graves,
Tenderly will I use you curling grass,
it may be you transpire from the breasts of young men,
It may be if I had known them I would have loved them,
It may be you are from old people, or from offspring taken soon out of their mothers' laps,
And here you are the mothers' laps.

This grass is very dark to be from the white heads of old mothers,
Darker than the colorless beards of old men,
Dark to come from under the faint red roofs of mouths.

O I perceive after all so many uttering tongues,
And I perceive they do not come from the roofs of mouths for nothing.

I wish I could translate the hints about the dead young men and women,
And the hints about old men and mothers, and the offspring taken soon out of their laps.

What do you think has become of the young and old men?
And what do you think has become of the women and children?

They are alive and well somewhere,
The smallest sprout shows there is really no death,
And if ever there was it led forward life, and does not wait
And ceas'd the moment life appeared.

All goes onward and outward, nothing collapses,
And to die is different from what any one supposed, and luckier.

I'm not quite sure what to make of this.   The opening of the poem asks about the various ways to describe grass and lists some of them.  Then it says that it 'seems to me the beautiful uncut hair of graves' and the poem hits its stride. 
The grass then, is a connection to those buried under it.  We can't help thinking of them.  The young and old, women and children.  Whitman asks what has become of them.  They continue in some way, in the grass that is growing above them.  'The smallest sprout shows there is really no death,/And if ever there was it led forward life'.  It's all part of a cycle.
I recognize the very last line, 'And to die is different from what any one supposed, and luckier', because it is used in the movie 'Dead Again'.  We really don't know what lies beyond our lives.  We have beliefs, some of them quite strong but we don't know.  I don't know that the grass is much of an answer.