common comfrey vs comfrey

common comfrey and comfrey both are nouns.

Word	Noun	Adjective	Verb	Adverb
common comfrey	Yes	No	No	No
comfrey	Yes	No	No	No

As nouns, comfrey is a hypernym of common comfrey; that is, comfrey is a word with a broader meaning than common comfrey:

common comfrey: European herb having small white, pink or purple flowers; naturalized as a weed in North America
comfrey: perennial herbs of Europe and Iran; make rapidly growing groundcover for shaded areas

Other hypernyms of common comfrey include cumfrey.

common comfrey (noun)	comfrey (noun)
European herb having small white, pink or purple flowers; naturalized as a weed in North America	leaves make a popular tisane; young leaves used in salads or cooked
	perennial herbs of Europe and Iran; make rapidly growing groundcover for shaded areas