horsefly weed vs wild indigo

horsefly weed and wild indigo both are nouns.

Word	Noun	Adjective	Verb	Adverb
horsefly weed	Yes	No	No	No
wild indigo	Yes	No	No	No

As nouns, wild indigo is a hypernym of horsefly weed; that is, wild indigo is a word with a broader meaning than horsefly weed:

horsefly weed: much-branched erect herb with bright yellow flowers; distributed from Massachusetts to Florida
wild indigo: any of several plants of the genus Baptisia

Other hypernyms of horsefly weed include false indigo.

horsefly weed (noun)	wild indigo (noun)
much-branched erect herb with bright yellow flowers; distributed from Massachusetts to Florida	any of several plants of the genus Baptisia