The article linked as the source (http://www.carrotmuseum.co.uk/history5.html http://www.carrotmuseum.co.uk/history5.html) actually says that the William of Ora

The article linked as the source (http://www.carrotmuseum.co.uk/history5.html http://www.carrotmuseum.co.uk/history5.html) actually says that the William of Orange story is probably apocryphal: "Though the stabilised orange carrot does date from around seventeenth century Netherlands, it is unlikely that honouring William of Orange had anything to do with it"