The most tender species of the Genus, Helleborus lividus, is native on the Mediterranean island of Majorca and might be a possibility. It's propagation and cultivation (in Britain) is outlined on Graham Rice's website(link below). The plants are sometimes available from some of the specialty nurseries, but the only seed sources I've seen, have been European.
Rb

Here is a link that might be useful: Helleborus lividus

Hi semoria,

Where do you live? In some zone 11 gardens you can probably grow all hellebores successfully. For germination you may want to do it artificially rather than in the garden (look up some of the old threads here related to "Elizabeth Town" or "ET seeds". Hellebore seeds are very easy to germinate although a bit slow at times.). H. argutifolius is also mediterranean. H. foetidus would also work just fine. The three mentioned are all stemmed so are very different than most other hellebores. They don't really need a rest period in winter at all. Little is known about this topic actually, but I know people who successfully grow them in southern California with irrigation (even Helleborus x hybridus), so it probably won't be a problem. Do it and let us know your results. It will be a fun and important experiment related to hellebore culture. In some gardens they will bloom on and off for the whole year. They are only known primarily as winter/spring plants because that is their natural cycle, but I suspect if given a 12 hour light/12 hour dark cycle (or something similar) and fairly even temps they would never stop putting out new growth.