pigeon pea vs pigeon-pea plant

pigeon pea and pigeon-pea plant both are nouns.

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

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

pigeon pea and pigeon-pea plant: tropical woody herb with showy yellow flowers and flat pods; much cultivated in the tropics

Other synonyms of pigeon pea include cajan pea, Cajanus cajan, catjang pea, dahl, dhal, red gram.

pigeon pea (noun)	pigeon-pea plant (noun)
small highly nutritious seed of the tropical pigeon-pea plant	tropical woody herb with showy yellow flowers and flat pods; much cultivated in the tropics
tropical woody herb with showy yellow flowers and flat pods; much cultivated in the tropics