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I've never tried to grow Aristolochia californica but...
They are native to the areas of California I grew up in: Sacramento Valley, Coast and Foothills - areas that get freezing temps but not much below that. The seeds have the reputation of taking between 2 months to 2 years to germinate. I have never seen them growing anyplace else suggesting that they need some pretty specific conditions to germinate.
My best guess is that Aristolochia californica does need a chill period to germinate well but that chill period is temps below 40. Put the package in the refrigerator for the winter or plant them in pots and leave them outside for the winter. Of coarse, that last suggestion depends upon where you live. They are native to zones 8 - 10. Also, I have only seen them growing in shady damp situations.
Daisy
