garden pea plant vs pea plant

garden pea plant and pea plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
garden pea plant	Yes	No	No	No
pea plant	Yes	No	No	No

As nouns, pea plant is a hypernym of garden pea plant; that is, pea plant is a word with a broader meaning than garden pea plant:

garden pea plant: plant producing peas usually eaten fresh rather than dried
pea plant: a leguminous plant of the genus Pisum with small white flowers and long green pods containing edible green seeds

Other hypernyms of garden pea plant include pea.

garden pea plant (noun)	pea plant (noun)
plant producing peas usually eaten fresh rather than dried	a leguminous plant of the genus Pisum with small white flowers and long green pods containing edible green seeds