Not possible further south, either it seems! Mine never have lost all their leaves. They stop growing and blooming usually in December and January, but start right up again after the short 'pout period' when a cold night knocks them back. Last year, mild winter, I had blooms every month of the year.
I'm guessing some places have more nematodes than others, too. They don't seem to like a high organic content in the soil, so closer to the beach where there's more sand and less humus is their favorite place.
