foliage vs plant organ

foliage and plant organ both are nouns.

Word	Noun	Adjective	Verb	Adverb
foliage	Yes	No	No	No
plant organ	Yes	No	No	No

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

foliage: the main organ of photosynthesis and transpiration in higher plants
plant organ: a functional and structural unit of a plant or fungus

foliage (noun)	plant organ (noun)
(architecture) leaf-like architectural ornament	a functional and structural unit of a plant or fungus
the main organ of photosynthesis and transpiration in higher plants