Many people here plant the seeds in the spring, especially if they once gardened up north, but they are a cool weather winter annual here. After all that rain, vast numbers of self sown nasturtium seeds from last spring are popping up in two street beds and should grow like crazy after this first wave of cooler weather coming this weekend. My favorite annual winter flower by far, edible too. The paradox is that a hard frost or freeze (more common in rural areas) can kill them. My favorite variety since the 80s is 'Dwarf Jewel Mix', which can be gotten by the pound from a great company in Golden, Colorado, that I've dealt with happily since the 1990s, Applewood Seeds Company.

http://www.applewoodseed.com/