blueweed vs blue thistle

blueweed and blue thistle both are nouns.

Word	Noun	Adjective	Verb	Adverb
blueweed	Yes	No	No	No
blue thistle	Yes	No	No	No

As nouns, blueweed and blue thistle are synonyms defined as:

blueweed and blue thistle: a coarse prickly European weed with spikes of blue flowers; naturalized in United States

Other synonyms of blueweed include blue devil, Echium vulgare, viper's bugloss.

blueweed (noun)	blue thistle (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