houseplant vs plant life

houseplant and plant life both are nouns.

Word	Noun	Adjective	Verb	Adverb
houseplant	Yes	No	No	No
plant life	Yes	No	No	No

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

houseplant: any of a variety of plants grown indoors for decorative purposes
plant life: (botany) a living organism lacking the power of locomotion

Other hypernyms of houseplant include flora, plant.

houseplant (noun)	plant life (noun)
any of a variety of plants grown indoors for decorative purposes	(botany) a living organism lacking the power of locomotion