It seems to vary from species to species, but, since it flowers so infrequently, there's not a good reference list to go by. I've typically heard 3-12 months, and your chances of germination improve if you keep it in the refrigerator. Even if you are able to plant it immediately after collecting it, your germination rate will probably improve by 6 weeks of chilling in the refrigerator.

Isn't that interesting...Cool, thanks!