sweet pea vs sweetpea

sweet pea and sweetpea both are nouns.

Word	Noun	Adjective	Verb	Adverb
sweet pea	Yes	No	No	No
sweetpea	Yes	No	No	No

As nouns, sweet pea and sweetpea are synonyms defined as:

sweet pea and sweetpea: climbing garden plant having fragrant pastel-colored flowers

Other synonyms of sweet pea include Lathyrus odoratus.

sweet pea (noun)	sweetpea (noun)
climbing garden plant having fragrant pastel-colored flowers	climbing garden plant having fragrant pastel-colored flowers