river red gum vs river gum

river red gum and river gum both are nouns.

Word	Noun	Adjective	Verb	Adverb
river red gum	Yes	No	No	No
river gum	Yes	No	No	No

As nouns, river red gum and river gum are synonyms defined as:

river red gum and river gum: somewhat crooked red gum tree growing chiefly along rivers; has durable reddish lumber used in heavy construction

Other synonyms of river red gum include Eucalyptus camaldulensis, Eucalyptus rostrata.

river red gum (noun)	river gum (noun)
somewhat crooked red gum tree growing chiefly along rivers; has durable reddish lumber used in heavy construction	somewhat crooked red gum tree growing chiefly along rivers; has durable reddish lumber used in heavy construction