welted thistle vs Carduus crispus

welted thistle and Carduus crispus both are nouns.

Word	Noun	Adjective	Verb	Adverb
welted thistle	Yes	No	No	No
Carduus crispus	Yes	No	No	No

As nouns, welted thistle and Carduus crispus are synonyms defined as:

welted thistle and Carduus crispus: European biennial introduced in North America having flower heads in crowded clusters at ends of branches

welted thistle (noun)	Carduus crispus (noun)
European biennial introduced in North America having flower heads in crowded clusters at ends of branches	European biennial introduced in North America having flower heads in crowded clusters at ends of branches