I am analyzing the scansion and literary devices of this poem, and do not understand two things:

Why he switches from iambic tetrameter to trochaic tetrameter in lines 3,6,8,13,14,16,17,19

and

What the last line means:
"The garland breifer than a girl's"

Any help would be much appreciated.

Erica

The change in meter is a device used frequently by poets. It would be dull to maintain the same meter throughout a poem. In particular, a poet will change the speed of a poem by changing the meter. Consider how much quicker mana and boy feels on the tongue as you say the line than 'and home we bought you shoulder high', the dropping of a syllable adds to the feeling of quickness.

As to the garland, well the head is small relative to where a girl may wear a garland!