They grow like weeds. The odd shaped bolus contains hundreds of flat seeds in 6 sections, and most of them grow if given a bit of dirt and water. I foolishly threw some in the mulch pile and now I pull them out everywhere I mulched. The seedlings also seem to be a bit more frost resistant than a mature vine. I noticed some of the ones growing in the bed with Musa basjoo that still have green leaves, while the mature vines took a hit with the frosts we had.

Still, they are one of my favorite vines and I encourage their use. They are a pain if you try for a formal look, but if you have a building that needs "walls" (gazebos, etc), they are hard to beat for a carefree solid wall of green.

At least for the couple species I've tried from seed, seeds are supposed to be placed on top of moist soil, not buried, as they need light to germinate. Keep the soil moist (easiest by covering the whole thing with plastic) and be patient--Aristolochia seeds can be slow.