This North American climber seems to be the most commonly, commercial sold subg. Siphisia species.

In fact, most of the hardy Aristolochia plants sold by local nurseries (even if labelled A. macrophylla or durior, etc.) often turn out to be this species.

However, Aristolochia tomentosa can easily be told apart from all its close relatives by the dense pubescence of all green parts, especially young and fleshy shoots.