king orange vs orange tree

king orange and orange tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
king orange	Yes	No	No	No
orange tree	Yes	No	No	No

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

king orange: large citrus tree having large sweet deep orange fruit that is easily peeled; widely cultivated in Florida
orange tree: any citrus tree bearing oranges

Other hypernyms of king orange include orange.

king orange (noun)	orange tree (noun)
large citrus tree having large sweet deep orange fruit that is easily peeled; widely cultivated in Florida	any citrus tree bearing oranges