sour gum vs tupelo tree

sour gum and tupelo tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
sour gum	Yes	No	No	No
tupelo tree	Yes	No	No	No

As nouns, tupelo tree is a hypernym of sour gum; that is, tupelo tree is a word with a broader meaning than sour gum:

sour gum: columnar tree of eastern North America having horizontal limbs and small leaves that emerge late in spring and have brilliant color in early fall
tupelo tree: any of several gum trees of swampy areas of North America

Other hypernyms of sour gum include tupelo.

sour gum (noun)	tupelo tree (noun)
columnar tree of eastern North America having horizontal limbs and small leaves that emerge late in spring and have brilliant color in early fall	any of several gum trees of swampy areas of North America