Are you quite certain it's not Wordsworth's "Intimations of Immortality"

Intimations of Immortality, Wm Wordsworth

There was a time when meadow, grove and stream,
The earth, and every common sight, to me did seem
Appareled in celestial light,
The glory and freshness of a dream.
It is not now as it hath been of yore
       Turn wheresoer I may,
       By night or day,
The things which I have seen I now can see no more.
The rainbow comes and goes,
And lovely is the Rose.
The sunshine is a glorious birth.
 But yet I know, whereer I go,
That there hath passed away a glory from the earth.
Wither is fled the visionary gleam?
Where is it now, the glory and the dream?
Our birth is but a sleep and a forgetting:
The soul that rises with us, our lifes star,
       Hath had elsewhere its setting,
       And cometh from afar.
Not in entire forgetfulness,
And not in utter nakedness,
But trailing clouds of glory do we come
       From God, who is our home.
Heaven lies about us in our infancy!
Shades of the prison-house begin to close
       Upon the growing boy...
Though nothing can bring back the hour
Of splendor in the grass, of glory in the flower...
Thanks to the human heart by which we live,
Thanks to its tenderness, its joys, and fear,
To me the meanest flower that blows can give
Thoughts that do often lie too deep for tears.

Is this it?

http://www.filmsite.org/sple.html

The film's title is taken from English romantic William Wordsworth's 1807 Ode, Intimations of Immortality from Reflections of Early Childhood, some of which is quoted here:


Though nothing can bring back the hour
Of splendor in the grass, of glory in the flower
We will grieve not, but rather find
Strength in what remains behind.

Whitman's book, and iirc poem, were called "Leaves of Grass"

Splendor in The Grass



What though the radiance which was once so bright

Be now for ever taken from my sight,

Though nothing can bring back the hour

Of splendor in the grass, of glory in the flower

We will grieve not, rather find

Strength in what remains behind;

In the primal sympathy

Which having been must ever be;

In the soothing thoughts that spring

Out of human suffering;

In the faith that looks through death,

In years that bring the philosophic mind.