What type of poem--ballad, free verse, etc.--is "Full Moon and Little Frieda" by Ted Hughes?

Ted Hughes is considered a modern poet, so it's not
surprising to know that he wrote this in a relatively modern format.  "Full Moon and
Little Frieda" is written in free verse.  Free verse is a poetic form with virtually no
rules.  It doesn't have to use rhyme, and in fact free verse poems rarely do.  There are
no set line lengths or rhythms, either.  Instead, poem written in free verse form is
generally more about the varied cadence of the words matching the cadence or flow of the
ideas.  In this poem, the following lines help demonstrate the cadence of sound and
meaning:

Cows
are going home in the lane there, looping the hedges with their warm
wreaths
of breath -

The "Cows" line
is a long, meandering kind of line, indicative of the cows slowly wandering their way
home; the "wreaths" line is short, like a puff of warm breath expelled on a cold day. 
The free verse form allows such diversity in lines and rhythms.