fertilizer vs plant food

fertilizer and plant food both are nouns.

Word	Noun	Adjective	Verb	Adverb
fertilizer	Yes	No	No	No
plant food	Yes	No	No	No

As nouns, fertilizer and plant food are synonyms defined as:

fertilizer and plant food: any substance such as manure or a mixture of nitrates used to make soil more fertile

Other synonyms of fertilizer include fertiliser.

fertilizer (noun)	plant food (noun)
any substance such as manure or a mixture of nitrates used to make soil more fertile	any substance such as manure or a mixture of nitrates used to make soil more fertile