wire grass vs broom grass

wire grass and broom grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
wire grass	Yes	No	No	No
broom grass	Yes	No	No	No

As nouns, broom grass is a hypernym of wire grass; that is, broom grass is a word with a broader meaning than wire grass:

wire grass: handsome hardy North American grass with foliage turning pale bronze in autumn
broom grass: any of several grasses of the genus Andropogon; used in broom making

wire grass (noun)	broom grass (noun)
coarse annual grass having fingerlike spikes of flowers; native to Old World tropics; a naturalized weed elsewhere	any of several grasses of the genus Andropogon; used in broom making
handsome hardy North American grass with foliage turning pale bronze in autumn