indigo broom vs rattle weed

indigo broom and rattle weed both are nouns.

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

As nouns, indigo broom and rattle weed are synonyms defined as:

indigo broom and rattle weed: much-branched erect herb with bright yellow flowers; distributed from Massachusetts to Florida

Other synonyms of indigo broom include Baptisia tinctoria, horsefly weed.

indigo broom (noun)	rattle weed (noun)
much-branched erect herb with bright yellow flowers; distributed from Massachusetts to Florida	much-branched erect herb with bright yellow flowers; distributed from Massachusetts to Florida