rattle weed vs wild indigo

rattle weed and wild indigo both are nouns.

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

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

rattle 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 rattle weed include false indigo.

rattle 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