Analysis of On The Reed (From The Greek)

I was of late a barren plant,
Useless, insignificant,
Nor fig, nor grape, nor apple bore,
A native of the marshy shore;
But, gather'd for poetic use,
And plunged into a sable juice,
Of which my modicum I sip
With narrow mouth and slender lip,
At once, although by nature dumb,
All eloquent I have become,
And speak with fluency untired,
As if by Phoebus' self inspired.