Although we have the word haricot in the dictionaries, the Dictionnaire Jersiais-Français comments that it is a recent borrowing from French, and it hasn’t supplanted the various indigenous words. And it turns out that the word haricot has not had a long history in French of being applied to beans – which explains why Jèrriais hasn’t inherited it from a common Romance word stock (indeed the application of haricot to beans appears to post-date the implantation of French in Canada). Of course, one might even speculate that English had borrowed the word first and the influence of trade and menus had brought the word into Jersey by the back door so to speak. So much of the history of the word haricot is speculation and an interesting post at Polyglot Vegetarian delves into the evidence and the arguments. Languagehat discusses further.
Since it is speculated that the etymology of haricot is ultimately Germanic (unless those holding out for an Aztec origin are correct), might there be a connection to our Norse-derived hadgi?