[ofrzeta]

It seems to be specific variety called Brassica oleracea longata (mentioned in the article) although in some places (https://www.victoriananursery.co.uk/Walking-Stick-Cabbage-Se...) it's called Brassica oleracea palmifolia which is a more widely known variety (cavolo nero in Italian).

How is it with plant genetics / breeding and taxonomy? When do you assert that something's a specific variety and apply a name to it?