wall pepper vs stonecrop

wall pepper and stonecrop both are nouns.

Word	Noun	Adjective	Verb	Adverb
wall pepper	Yes	No	No	No
stonecrop	Yes	No	No	No

As nouns, stonecrop is a hypernym of wall pepper; that is, stonecrop is a word with a broader meaning than wall pepper:

wall pepper: mossy European creeping sedum with yellow flowers; widely introduced as a ground cover
stonecrop: any of various northern temperate plants of the genus Sedum having fleshy leaves and red or yellow or white flowers

wall pepper (noun)	stonecrop (noun)
mossy European creeping sedum with yellow flowers; widely introduced as a ground cover	any of various northern temperate plants of the genus Sedum having fleshy leaves and red or yellow or white flowers