flower bed vs tulip bed

flower bed and tulip bed both are nouns.

Word	Noun	Adjective	Verb	Adverb
flower bed	Yes	No	No	No
tulip bed	Yes	No	No	No

As nouns, tulip bed is a hyponym of flower bed; that is, tulip bed is a word with a more specific, narrower meaning than flower bed:

Other hyponyms of flower bed include bed of roses, rose bed.

flower bed (noun)	tulip bed (noun)
a bed in which flowers are growing	a flowerbed in which tulips are growing