bunchgrass vs bunch grass

bunchgrass and bunch grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
bunchgrass	Yes	No	No	No
bunch grass	Yes	No	No	No

As nouns, bunchgrass and bunch grass are synonyms defined as:

bunchgrass and bunch grass: any of various grasses of many genera that grow in tufts or clumps rather than forming a sod or mat; chiefly of western United States

bunchgrass (noun)	bunch grass (noun)
any of various grasses of many genera that grow in tufts or clumps rather than forming a sod or mat; chiefly of western United States	any of various grasses of many genera that grow in tufts or clumps rather than forming a sod or mat; chiefly of western United States