There
 are a number of ways you could categorize the poem.  It's free verse, 
since it doesn't use rhyme or meter.  It's a nature poem obviously.  And it's a 
lyric poem, which is usually defined as a short poem that describes 
something or expresses thoughts and feelings (as opposed to a narrative 
poem, which is like a short story or a novel in verse, a longer poem 
that tells a whole story).