blue thistle vs viper's bugloss

blue thistle and viper's bugloss both are nouns.

Word	Noun	Adjective	Verb	Adverb
blue thistle	Yes	No	No	No
viper's bugloss	Yes	No	No	No

As nouns, blue thistle and viper's bugloss are synonyms defined as:

blue thistle and viper's bugloss: a coarse prickly European weed with spikes of blue flowers; naturalized in United States

Other synonyms of blue thistle include blue devil, blueweed, Echium vulgare.

blue thistle (noun)	viper's bugloss (noun)
a coarse prickly European weed with spikes of blue flowers; naturalized in United States	a coarse prickly European weed with spikes of blue flowers; naturalized in United States