feather reed grass vs feathertop

feather reed grass and feathertop both are nouns.

Word	Noun	Adjective	Verb	Adverb
feather reed grass	Yes	No	No	No
feathertop	Yes	No	No	No

As nouns, feather reed grass and feathertop are synonyms defined as:

Other synonyms of feather reed grass include Calamagrostis acutiflora.

feather reed grass (noun)	feathertop (noun)
a variety of reed grass	northeastern tropical African plant having feathery panicles
	a variety of reed grass