Sporobolus poiretii vs dropseed

Sporobolus poiretii and dropseed both are nouns.

Word	Noun	Adjective	Verb	Adverb
Sporobolus poiretii	Yes	No	No	No
dropseed	Yes	No	No	No

As nouns, dropseed is a hypernym of Sporobolus poiretii; that is, dropseed is a word with a broader meaning than Sporobolus poiretii:

Sporobolus poiretii: grass native to West Indies but common in southern United States having tufted wiry stems often infested with a dark fungus
dropseed: a grass of the genus Sporobolus

Other hypernyms of Sporobolus poiretii include drop-seed.

Sporobolus poiretii (noun)	dropseed (noun)
grass native to West Indies but common in southern United States having tufted wiry stems often infested with a dark fungus	a grass of the genus Sporobolus