Grindelia squarrosa vs tarweed

Grindelia squarrosa and tarweed both are nouns.

Word	Noun	Adjective	Verb	Adverb
Grindelia squarrosa	Yes	No	No	No
tarweed	Yes	No	No	No

As nouns, tarweed is a hypernym of Grindelia squarrosa; that is, tarweed is a word with a broader meaning than Grindelia squarrosa:

Grindelia squarrosa: perennial gumweed of western and central North America
tarweed: any of various western American plants of the genus Grindelia having resinous leaves and stems formerly used medicinally; often poisonous to livestock

Other hypernyms of Grindelia squarrosa include gum plant, gumweed, rosinweed.

Grindelia squarrosa (noun)	tarweed (noun)
perennial gumweed of western and central North America	any of various resinous glandular plants of the genus Madia; of western North and South America
	any of various western American plants of the genus Grindelia having resinous leaves and stems formerly used medicinally; often poisonous to livestock