How can poetry by Emily Dickinson (especially "A narrow fellow in the grass") be considered Romanticism?

Romanticism (with a capital "R") centered around the aesthetics of nature, and often compared the growth and development of animal and plant life to human life and behavior. 

We see all of this at work in "A narrow fellow in the grass."  Here is the poem in its entirety:

A narrow Fellow in the Grass
Occasionally rides--
You may have met Him--
did you not
His notice sudden is--

The Grass divides as with a Comb--
A spotted shaft is seen--
And then it closes at your feet
And opens further on--

He likes a Boggy Acre
A Floor too cool for Corn--
Yet when a Boy, and Barefoot--
I more than once at Noon

Have passed, I thought, a Whip lash
Unbraiding in the Sun
When stooping to secure it
It wrinkled, and was gone--

Several of Nature's People
I know, and they know me--
I feel for them a transport
Of cordiality--

But never met this Fellow
Attended, or alone
Without a tighter breathing
And Zero at the Bone--

What surprises a good number of students is that this poem, a reflection of nature, is a reflection of human sexuality.  Read the poem in terms of male and female organs:  "The Grass divides as with a Comb-- /  A spotted shaft is seen, " an later, the sexual act completed, "It wrinkled, and was gone." 

Romantic poets did not shy away from the fullness of the human experience.  Keats, Wordsworth, Shelley, and Blake were just a few who also lauded the physical.