blackseed vs dropseed

blackseed and dropseed both are nouns.

Word	Noun	Adjective	Verb	Adverb
blackseed	Yes	No	No	No
dropseed	Yes	No	No	No

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

blackseed: 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 blackseed include drop-seed.

blackseed (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