Culvers root vs Culver's root

Culvers root and Culver's root both are nouns.

Word	Noun	Adjective	Verb	Adverb
Culvers root	Yes	No	No	No
Culver's root	Yes	No	No	No

As nouns, Culvers root and Culver's root are synonyms defined as:

Culvers root and Culver's root: a tall perennial herb having spikes of small white or purple flowers; common in eastern North America

Other synonyms of Culvers root include Culver's physic, Culvers physic, Veronicastrum virginicum, whorlywort.

Culvers root (noun)	Culver's root (noun)
a tall perennial herb having spikes of small white or purple flowers; common in eastern North America	a tall perennial herb having spikes of small white or purple flowers; common in eastern North America