Pelargonium is an amazing genus, and too poorly known by serious plantspeople. Most of the few hundred species are quite different than the familiar red "geranium" so commonly grown in containers and gardens. Perhaps the largest "section" of the genus is section Hoarea, which consists of generally small rosette forming plants with tuberous roots and a winter growing cycle. Flower colors can range from white to pinks, purples, maroons, lavendars, and even yellow in several species. They come from the old Cape Province of South Africa, with some outliers in Namibia. They are collector's plants for sure, and hard to come by. They are not all that hard to grow if you understand their natural requirements: water during their growing period from fall to spring, a dry spot to store the pot during the summer dormancy, and bright enough light for good growth. Fungicide is good to have on hand for emergencies should root rot or botrytis fungus show up. Most will grow under flourescent plant lights, indeed that is how I grew this one until it got warm enough to place it on a terrace outdoors where it gets a few hours of sun. If you are lucky enough to have a cool greenhouse, they will grow even better, as they might also do under cover (in case of excessive rain) in California. Careful hand pollination of the flowers results in seed, although I got much more seed set when I grew then in greenhouses in the past at the NYBG or at Cornell. Many species in this section will flower their first year from seed, if started in early winter or late fall. Most flower when the leaves begin to die back, though some, like P. incrassatum, flower with the foliage present. The species shown came to me without a name many years ago, from a collector in South Africa. Many species still remain to be formally described and named, and variation within a species is quite pronounced in many pelargonium species that I have grown in the past.
One source which carries quite a few of these species, and pretty much the only one I know of in this country that has more than one or two species, is Arid Lands greenhouses. They send the plants bareroot but they recover quickly and plants I have gotten from them do very well. They are also very reasonably priced for such rarities. For those wanting to try seed, aside from specialist societies (such as the Geraniaceae Group, which I must get around to rejoining, its a great little society of knowledgable individuals), Silverhill Seeds in South Africa has a good list of pelargonium seeds, including a few Hoarea types.