Aristolochia watsonii (Watson's Dutchman's pipe, southwestern pipevine, Indian root, snakeroot) is a perennial plant[2] in the birthwort family (Aristolochiaceae), found growing among plants of the Arizona Uplands in the Sonoran Desert.[3]: 138 The plant is inconspicuous,[3]: 138 small and hard to spot, but can be found by following the pipevine swallowtail (blue swallowtail, Battus philenor) which lays eggs on it.[2]
It grows as vine with scrambling stems that create a dense, tangled mat over the years when growing on open ground.[2][3]: 138
According to one source, stems are 150 to 450 mm (6 to 18 in) long, with greenish-brown arrowhead-shaped 5 to 65 mm (1⁄4 to 2+1⁄2 in) leaves.[3]: 138 Another source states stems can reach 0.9 m (3 ft), in dense mats that are 0.3 to 0.6 m (1 to 2 ft) wide.[2] It drops its leaves in the fall and winter (cold-deciduous), and loses stems as well as leaves in a freeze.[2] In full sun and drought conditions, leaves turn from green to purple-brown.[2]
It has "bizarre" looking, musky-smelling flowers, which resemble the ear of a rodent.[3]: 138 It blooms from April to October. 25 to 40 mm (1 to 1+1⁄2 in) flowers are shaped like a rodent's ear[2][3]: 138 are green or burgundy-brown outside to the ear rim, then green speckled with burgundy-brown inside, with hairs on the opening ear rim.[3]: 138 Flowers last 1–2 days.[2]
Fruits are capsules having five vertical ribs with triangular-shaped flat and black seeds in each of five compartments.[2]
Flowers shaped and smelling like a rodent's ear attract small blood-sucking flies, which are deceived by the appearance and odor and get trapped in the convoluted flower form for a day, then escape to pollinate another plant.[2][3]: 138 It attracts the pipevine swallowtail,[4] and is where the butterfly gets its distasteful toxins that protect the butterfly from predation.[2] The caterpillar may eat all of the leaves on a plant, but they then grow back.[2]
All parts of this plant are toxic to humans.[2][5]
It is found from Arizona to western Texas, in mountains at elevations from 600 to 1,400 m (2,000 to 4,500 ft).[3]: 138
Native Americans believed it could be used to treat snakebites, hence its common names Indian root or snakeroot.[3]: 138 It is currently found in some nurseries that feature native plants as it is a good landscape plant in a butterfly garden.[6]
Aristolochia watsonii (Watson's Dutchman's pipe, southwestern pipevine, Indian root, snakeroot) is a perennial plant in the birthwort family (Aristolochiaceae), found growing among plants of the Arizona Uplands in the Sonoran Desert.: 138 The plant is inconspicuous,: 138 small and hard to spot, but can be found by following the pipevine swallowtail (blue swallowtail, Battus philenor) which lays eggs on it.
