common tobacco vs tobacco plant

common tobacco and tobacco plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
common tobacco	Yes	No	No	No
tobacco plant	Yes	No	No	No

As nouns, tobacco plant is a hypernym of common tobacco; that is, tobacco plant is a word with a broader meaning than common tobacco:

common tobacco: tall erect South American herb with large ovate leaves and terminal clusters of tubular white or pink flowers; cultivated for its leaves
tobacco plant: aromatic annual or perennial herbs and shrubs

Other hypernyms of common tobacco include tobacco.

common tobacco (noun)	tobacco plant (noun)
tall erect South American herb with large ovate leaves and terminal clusters of tubular white or pink flowers; cultivated for its leaves	aromatic annual or perennial herbs and shrubs