sweet calamus vs swamp plant

sweet calamus and swamp plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
sweet calamus	Yes	No	No	No
swamp plant	Yes	No	No	No

As nouns, swamp plant is a hypernym of sweet calamus; that is, swamp plant is a word with a broader meaning than sweet calamus:

sweet calamus: perennial marsh plant having swordlike leaves and aromatic roots
swamp plant: a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath

Other hypernyms of sweet calamus include bog plant, marsh plant.

sweet calamus (noun)	swamp plant (noun)
perennial marsh plant having swordlike leaves and aromatic roots	a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath