Aristolochia watsonii
# Aristolochia watsonii

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.

## Description

### Growth pattern

It grows as vine with scrambling stems that create a dense, tangled mat over the years when growing on open $ground.^{:138}$

### Roots, stems, and leaves

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) $leaves.^{:138}$ 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. It drops its leaves in the fall and winter (cold-deciduous), and loses stems as well as leaves in a freeze. In full sun and drought conditions, leaves turn from green to purple-brown.

### Inflorescence and fruit

It has "bizarre" looking, musky-smelling flowers, which resemble the ear of a $rodent.^{:138}$ It blooms from April to October. 25 to 40 mm (1 to 1+1⁄2 in) flowers are shaped like a rodent's $ear^{:138}$ are green or burgundy-brown outside to the ear rim, then green speckled with burgundy-brown inside, with hairs on the opening ear $rim.^{:138}$ Flowers last 1–2 days.

Fruits are capsules having five vertical ribs with triangular-shaped flat and black seeds in each of five compartments.

### Ecological interactions

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 $plant.^{:138}$ It attracts the pipevine swallowtail, and is where the butterfly gets its distasteful toxins that protect the butterfly from predation. The caterpillar may eat all of the leaves on a plant, but they then grow back.

### Toxicity

All parts of this plant are toxic to humans.

## Habitat and Distribution

It is found from Arizona to western Texas, in mountains at elevations from 600 to 1,400 m (2,000 to 4,500 $ft).^{:138}$

## Human use

Native Americans believed it could be used to treat snakebites, hence its common names Indian root or $snakeroot.^{:138}$ It is currently found in some nurseries that feature native plants as it is a good landscape plant in a butterfly garden.

