Read the poem “Nothing Gold Can Stay,” by Robert Frost.

Nothing Gold Can Stay

Nature's first green is gold,
Her hardest hue to hold.
Her early leaf's a flower;
But only so an hour.
Then leaf subsides to leaf.
So Eden sank to grief,
So dawn goes down to day.
Nothing gold can stay.

Which line of the poem expresses the theme that youth passes quickly?

So Eden sank to grief

Nature's first green is gold

Then leaf subsides to leaf

But only so an hour

"But only so an hour" is the line that expresses the theme that youth passes quickly. It emphasizes the fleeting nature of beauty and youth, and how quickly they can fade away.