Rocky Mountain dogbane vs Apocynum pumilum

Rocky Mountain dogbane and Apocynum pumilum both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rocky Mountain dogbane	Yes	No	No	No
Apocynum pumilum	Yes	No	No	No

As nouns, Rocky Mountain dogbane and Apocynum pumilum are synonyms defined as:

Rocky Mountain dogbane and Apocynum pumilum: North American plant similar to common dogbane

Rocky Mountain dogbane (noun)	Apocynum pumilum (noun)
North American plant similar to common dogbane	North American plant similar to common dogbane