head cabbage plant vs Brassica oleracea capitata

head cabbage plant and Brassica oleracea capitata both are nouns.

Word	Noun	Adjective	Verb	Adverb
head cabbage plant	Yes	No	No	No
Brassica oleracea capitata	Yes	No	No	No

As nouns, head cabbage plant and Brassica oleracea capitata are synonyms defined as:

head cabbage plant and Brassica oleracea capitata: any of various cultivated cabbage plants having a short thick stalk and large compact head of edible usually green leaves

Other synonyms of head cabbage plant include head cabbage.

head cabbage plant (noun)	Brassica oleracea capitata (noun)
any of various cultivated cabbage plants having a short thick stalk and large compact head of edible usually green leaves	any of various cultivated cabbage plants having a short thick stalk and large compact head of edible usually green leaves