white mulberry vs mulberry tree

white mulberry and mulberry tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
white mulberry	Yes	No	No	No
mulberry tree	Yes	No	No	No

As nouns, mulberry tree is a hypernym of white mulberry; that is, mulberry tree is a word with a broader meaning than white mulberry:

white mulberry: Asiatic mulberry with white to pale red fruit; leaves used to feed silkworms
mulberry tree: any of several trees of the genus Morus having edible fruit that resembles the blackberry

Other hypernyms of white mulberry include mulberry.

white mulberry (noun)	mulberry tree (noun)
Asiatic mulberry with white to pale red fruit; leaves used to feed silkworms	any of several trees of the genus Morus having edible fruit that resembles the blackberry