Rhode Island bent vs bent-grass

Rhode Island bent and bent-grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rhode Island bent	Yes	No	No	No
bent-grass	Yes	No	No	No

As nouns, bent-grass is a hypernym of Rhode Island bent; that is, bent-grass is a word with a broader meaning than Rhode Island bent:

Rhode Island bent: common grass with slender stems and narrow leaves
bent-grass: grass for pastures and lawns especially bowling and putting greens

Other hypernyms of Rhode Island bent include bent, bent grass.

Rhode Island bent (noun)	bent-grass (noun)
common grass with slender stems and narrow leaves	grass for pastures and lawns especially bowling and putting greens