rowan tree vs mountain ash

rowan tree and mountain ash both are nouns.

Word	Noun	Adjective	Verb	Adverb
rowan tree	Yes	No	No	No
mountain ash	Yes	No	No	No

As nouns, mountain ash is a hypernym of rowan tree; that is, mountain ash is a word with a broader meaning than rowan tree:

rowan tree (noun)	mountain ash (noun)
Eurasian tree with orange-red berrylike fruits	any of various trees of the genus Sorbus
	low-growing ash of Texas
	tree having wood similar to the alpine ash; tallest tree in Australia and tallest hardwood in the world