field pea vs field-pea plant

field pea and field-pea plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
field pea	Yes	No	No	No
field-pea plant	Yes	No	No	No

As nouns, field pea and field-pea plant are synonyms defined as:

field pea and field-pea plant: variety of pea plant native to the Mediterranean region and North Africa and widely grown especially for forage

Other synonyms of field pea include Austrian winter pea, Pisum arvense, Pisum sativum arvense.

field pea (noun)	field-pea plant (noun)
coarse small-seeded pea often used as food when young and tender	variety of pea plant native to the Mediterranean region and North Africa and widely grown especially for forage
variety of pea plant native to the Mediterranean region and North Africa and widely grown especially for forage
seed of the field pea plant