western ragweed vs perennial ragweed

western ragweed and perennial ragweed both are nouns.

Word	Noun	Adjective	Verb	Adverb
western ragweed	Yes	No	No	No
perennial ragweed	Yes	No	No	No

As nouns, western ragweed and perennial ragweed are synonyms defined as:

western ragweed and perennial ragweed: coarse perennial ragweed with creeping roots of dry barren lands of southwestern United States and Mexico

Other synonyms of western ragweed include Ambrosia psilostachya.

western ragweed (noun)	perennial ragweed (noun)
coarse perennial ragweed with creeping roots of dry barren lands of southwestern United States and Mexico	coarse perennial ragweed with creeping roots of dry barren lands of southwestern United States and Mexico