silkgrass vs silk grass

silkgrass and silk grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
silkgrass	Yes	No	No	No
silk grass	Yes	No	No	No

As nouns, silkgrass and silk grass are synonyms defined as:

silkgrass and silk grass: valuable forage grass of dry upland areas and plains of western North America to northern Mexico

Other synonyms of silkgrass include Indian millet, mountain rice, Oryzopsis hymenoides.

silkgrass (noun)	silk grass (noun)
valuable forage grass of dry upland areas and plains of western North America to northern Mexico	valuable forage grass of dry upland areas and plains of western North America to northern Mexico