lyme grass vs Elymus

lyme grass and Elymus both are nouns.

Word	Noun	Adjective	Verb	Adverb
lyme grass	Yes	No	No	No
Elymus	Yes	No	No	No

lyme grass (noun)	Elymus (noun)
a grass of the genus Elymus	tall tufted perennial grasses (such as lyme grass or wild rye)