bent grass vs bent-grass

bent grass and bent-grass both are nouns.

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

As nouns, bent grass and bent-grass are synonyms defined as:

bent grass and bent-grass: grass for pastures and lawns especially bowling and putting greens

Other synonyms of bent grass include bent.

bent grass (noun)	bent-grass (noun)
grass for pastures and lawns especially bowling and putting greens	grass for pastures and lawns especially bowling and putting greens