Centaurea nigra vs lesser knapweed

Centaurea nigra and lesser knapweed both are nouns.

Word	Noun	Adjective	Verb	Adverb
Centaurea nigra	Yes	No	No	No
lesser knapweed	Yes	No	No	No

As nouns, Centaurea nigra and lesser knapweed are synonyms defined as:

Centaurea nigra and lesser knapweed: a weedy perennial with tough wiry stems and purple flowers; native to Europe but widely naturalized

Other synonyms of Centaurea nigra include black knapweed, hardheads.

Centaurea nigra (noun)	lesser knapweed (noun)
a weedy perennial with tough wiry stems and purple flowers; native to Europe but widely naturalized	a weedy perennial with tough wiry stems and purple flowers; native to Europe but widely naturalized