big-tree plum vs Prunus mexicana

big-tree plum and Prunus mexicana both are nouns.

Word	Noun	Adjective	Verb	Adverb
big-tree plum	Yes	No	No	No
Prunus mexicana	Yes	No	No	No

As nouns, big-tree plum and Prunus mexicana are synonyms defined as:

big-tree plum and Prunus mexicana: small tree of southwestern United States having purplish-red fruit sometimes cultivated as an ornamental for its large leaves

big-tree plum (noun)	Prunus mexicana (noun)
small tree of southwestern United States having purplish-red fruit sometimes cultivated as an ornamental for its large leaves	small tree of southwestern United States having purplish-red fruit sometimes cultivated as an ornamental for its large leaves