knob celery vs herbaceous plant

knob celery and herbaceous plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
knob celery	Yes	No	No	No
herbaceous plant	Yes	No	No	No

As nouns, herbaceous plant is a hypernym of knob celery; that is, herbaceous plant is a word with a broader meaning than knob celery:

knob celery: grown for its thickened edible aromatic root
herbaceous plant: a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests

Other hypernyms of knob celery include herb.

knob celery (noun)	herbaceous plant (noun)
grown for its thickened edible aromatic root	a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests