stone cress vs stonecress

stone cress and stonecress both are nouns.

Word	Noun	Adjective	Verb	Adverb
stone cress	Yes	No	No	No
stonecress	Yes	No	No	No

As nouns, stone cress and stonecress are synonyms defined as:

stone cress and stonecress: any Old World herb of the genus Aethionema; native of sunny limestone habitats

stone cress (noun)	stonecress (noun)
any Old World herb of the genus Aethionema; native of sunny limestone habitats	any Old World herb of the genus Aethionema; native of sunny limestone habitats