lesser spearwort vs swamp plant

lesser spearwort and swamp plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
lesser spearwort	Yes	No	No	No
swamp plant	Yes	No	No	No

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

lesser spearwort: semiaquatic Eurasian perennial crowfoot with leaves shaped like spears; naturalized in New Zealand
swamp plant: a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath

Other hypernyms of lesser spearwort include bog plant, marsh plant.

lesser spearwort (noun)	swamp plant (noun)
semiaquatic Eurasian perennial crowfoot with leaves shaped like spears; naturalized in New Zealand	a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath