black-eyed Susan vs genus Rudbeckia

black-eyed Susan and genus Rudbeckia both are nouns.

Word	Noun	Adjective	Verb	Adverb
black-eyed Susan	Yes	No	No	No
genus Rudbeckia	Yes	No	No	No

black-eyed Susan (noun)	genus Rudbeckia (noun)
the state flower of Maryland; of central and southeastern United States; having daisylike flowers with dark centers and yellow to orange rays	North American perennial herbs with showy cone-shaped flower heads
tropical African climbing plant having yellow flowers with a dark purple center
annual weedy herb with ephemeral yellow purple-eyed flowers; Old World tropics; naturalized as a weed in North America