Russian thistle vs Russian cactus

Russian thistle and Russian cactus both are nouns.

Word	Noun	Adjective	Verb	Adverb
Russian thistle	Yes	No	No	No
Russian cactus	Yes	No	No	No

As nouns, Russian thistle and Russian cactus are synonyms defined as:

Russian thistle and Russian cactus: prickly bushy Eurasian plant; a troublesome weed in central and western United States

Other synonyms of Russian thistle include Russian tumbleweed, Salsola kali tenuifolia, tumbleweed.

Russian thistle (noun)	Russian cactus (noun)
prickly bushy Eurasian plant; a troublesome weed in central and western United States	prickly bushy Eurasian plant; a troublesome weed in central and western United States