lesser spearwort vs marsh plant

lesser spearwort and marsh plant both are nouns.

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

As nouns, marsh plant is a hypernym of lesser spearwort; that is, marsh 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
marsh 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, swamp plant.

lesser spearwort (noun)	marsh 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