grey-leaf pine vs pine tree

grey-leaf pine and pine tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
grey-leaf pine	Yes	No	No	No
pine tree	Yes	No	No	No

As nouns, pine tree is a hypernym of grey-leaf pine; that is, pine tree is a word with a broader meaning than grey-leaf pine:

grey-leaf pine: medium-sized five-needled pine of southwestern California having long cylindrical cones
pine tree: a coniferous tree

Other hypernyms of grey-leaf pine include pine, true pine.

grey-leaf pine (noun)	pine tree (noun)
medium-sized five-needled pine of southwestern California having long cylindrical cones	a coniferous tree