Aristolochia flower. Aristolochia is the type genus of the extensive plant family Aristolochiaceae. Popular names by which it is known are birthwort, pipevine and Dutch pipe. It is an evergreen that thrives in varying climates worldwide, growing like a woody vine from a smooth and erect stem. The pinkish red flowers grow from the leaf axils and may reach a considerable size, up to and over 35 cm as in this example. Photographed in the hothouses of the Botanical Gardens in the Uithof, Utrecht.