flower bed vs bed of flowers

flower bed and bed of flowers both are nouns.

Word	Noun	Adjective	Verb	Adverb
flower bed	Yes	No	No	No
bed of flowers	Yes	No	No	No

As nouns, flower bed and bed of flowers are synonyms defined as:

Other synonyms of flower bed include flowerbed.

flower bed (noun)	bed of flowers (noun)
a bed in which flowers are growing	a bed in which flowers are growing