in Tucson, Phoenix,
Arizona and California

Gardening in Tucson, Phoenix, Arizona and California

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Aristolochia watsonii: Watson's Dutchman's Pipe / Desert Pipevine

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Form: A vine that, over several years, may create a dense, tangled mat of stems and leaves on open ground.
Lifespan: Perennial.
Leaf retention: Cold deciduous. Stems and leaves die in freezes.
Growth rate: Slow.
Mature Size: Vines up to 3' long form a dense green or purple-tinged brown mat, of stems and leaves, 1-2' wide and 1" high.
Flowers: Tiny, mouse-ear-shaped, green and brown flowers. Each flower lasts one or two days. The flowers give off an aroma like that of a rodent's ear. This attracts blood-sucking flies, which normally feed on the inside of rodent ears, and forces them to become pollinators.
Bloom: Spring and summer.
Fruit: A capsule with five vertical ribs containing stacks of flat, black, triangular seeds in five compartments.
Leaves: Small, green, usually slender, arrowhead shaped leaves, 1-1.5" long, which turn purple-brown in full sun and drought conditions.
Stems: No thorns.
Wildlife: A food plant of the Pipevine Swallowtail caterpillar which incorporates the plant's poison into its skin to ward off predators. This caterpillar can completely defoliate the plant, but the leaves will grow back.
Toxic / Danger: All parts of this plant are toxic.
Origin: Native to Arizona, New Mexico and Mexico.

Cultivation and Uses
USDA hardiness zones: 8-9, possibly greater.
Heat tolerant: Yes.
Drought tolerant: Yes.
Sun: Best in part shade, but tolerates full sun.
Water once established: Once every month or two. Supplemental water may improve growth. Soil should dry out between waterings.
Soil: Dry, low organic content, pH 6.6-7.5 (neutral).
Prune: Brush away dead leaves and stems after prolonged freeze.
Litter: Low.
Propagation: Seed.
Uses: To attract and propagate the Pipevine Swallowtail butterfly.

This plant is difficult to spot on open ground because of its small size. Follow the Pipevine Swallowtail butterfly to locate the plant.

The third picture from the top is an Aristolochia watsonii mat, 16x12", on an east-facing slope. The slope attenuates the afternoon sun and allows the mat to stay green.

The bottom picture is a healthy, 2' wide, Aristolochia watsonii mat in full sun and drought conditions on level ground. The root system is at least 8 years old. This plant, and the plant in the picture above, are 50' apart, sharing the same temperature and rainfall conditions.

These plants have become large because nearby lizards routinely search them for butterfly eggs and small caterpillars. The caterpillars are never allowed to get large enough to eat the whole plant and slow its root growth.

All photos taken in USDA hardiness zone 8b.

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Aristolochia watsonii: Desert Pipevine - flowers
The odd-shaped flowers have brown speckles.

Aristolochia watsonii: Desert Pipevine - seed pods with caterpillar
Two seed capsules can be seen at lower left and lower center. A third one is near the center.
The caterpillar is that of the Pipevine Swallowtail butterfly.

Aristolochia watsonii: Desert Pipevine mat

Aristolochia watsonii: Desert Pipevine mat