I've been noticing that some of my fellow Canadians habitually spell words such as "organise, organisation" "realise" recognise""authorise" instead "organize, organization" "realize" "recognize" "authorize." I've been told by other Canadians that Canadians use -ise and -ize interchangeably; both are considered correct as long as you choose one and be consistent. But that puzzles me because according to all Canadian dictionaries that I've looked at, the -ize spelling is prescribed. I thought the -ise would appear as a minor variant, but it doesn't appear at all in any Canadian dictionary. My question is: is the -ise really an acceptable variant in Canadian English? or is the -ize mandatory like in the US?
Margery Fee & Janice McAlpine, [Oxford] Guide to Canadian English Usage, second edition (2007) offers this discussion of -ize versus -ise verb endings in Canadian English:
-ize, -ise, -yze, -yse Where there is a choice between -ize and -ise Canadian writers, kike Americans, tend to to choose the endings with z. In fact, Canadian, American, and British writers all prefer -ize for recognize, civilize and civilization, organize and organization, realize and realization, and specialize and specialization. The British preference for -ise endings is an innovation rather than a longstanding spelling tradition. In Canada and Britain either spelling is usually considered correct, while in the United States the -ize endings are de rigueur.
Note, however, that Canadian, American, and British writers all use -ise for advertise, supervise, and surprise. For these words, the spelling with z is not an option.
So, according to Fee & McAlpine, some Canadians (and some British people) do use -ise endings for many words that most people in the United States would spell with an -ize ending.