japan clover vs bush clover

japan clover and bush clover both are nouns.

Word	Noun	Adjective	Verb	Adverb
japan clover	Yes	No	No	No
bush clover	Yes	No	No	No

As nouns, bush clover is a hypernym of japan clover; that is, bush clover is a word with a broader meaning than japan clover:

japan clover: an annual of tropical Asia naturalized in United States
bush clover: shrubby or herbaceous plants widely used for forage, soil improvement, and especially hay in southern United States

Other hypernyms of japan clover include lespedeza.

japan clover (noun)	bush clover (noun)
an annual of tropical Asia naturalized in United States	shrubby or herbaceous plants widely used for forage, soil improvement, and especially hay in southern United States