hemlock tree vs coniferous tree

hemlock tree and coniferous tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
hemlock tree	Yes	No	No	No
coniferous tree	Yes	No	No	No

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

hemlock tree: an evergreen tree, could refer to any one of a genus of conifers named Tsuga
coniferous tree: any gymnospermous tree or shrub bearing cones

Other hypernyms of hemlock tree include conifer.

hemlock tree (noun)	coniferous tree (noun)
an evergreen tree, could refer to any one of a genus of conifers named Tsuga	any gymnospermous tree or shrub bearing cones