Aristolochiaceae, Birthwort Family
The Aristolochiaceae or Birthwort family is a small family with only 7 genera and about 400 species. The type genus is Aristolochia. Species are mostly perennial herbs, subshrubs or woody vines. Leaves are alternate, simple, heart shaped (cordate), margins entire and without stipules. Flowers are in leaf axils, medium to large and bizarre looking with their unique bilateral symmetry. Flowers of this family have three sections; the utricle, tube and limb.
One species native to Central America and introduced in Florida, the Pelican Flower, Aristolochia grandiflora, has heart-shaped flowers 8 inches wide with "tails" up to 23 inches long. These peculiar flowers have evolved curious pollination strategies over the years to perfect insect pollination and some species avoid plant predation from herbivores. Many species of the genus Aristolochia and some of the genus Asarum, contain an acid, aristolochic acid, fatal to most plant predators.
There are approximately 600 species and 7 genera in Aristolochiaceae in the United States and parts of Canada; Aristolochia, Asarum and Hexastylis.
There is one species in Aristolochiaceae in Arizona, Aristolochia watsonii, Watson's Dutchman's Pipe.