Herbs , procumbent, to 0.5 m. Young stem smooth, glabrous. Leaves: petiole 0.4-1 cm. Leaf blade lanceolate, 8 × 5 cm, base strongly sagittate, sinus depth 0.5-2 cm, apex acuminate to acute; surfaces abaxially tomentose to tomentulose; venation pinnate. Inflorescences on new growth, axillary, solitary flowers; peduncle bracteolate, to 1 cm; bracteoles lanceolate, to 6 mm. Flowers: calyx brown-purple, straight to curved; utricle angled upward, ovoid to narrowly ellipsoid, 0.6-0.7 × 0.5 cm; syrinx tubular, 1.5 mm; tube angled upward, cylindric, 1 × 0.3 cm; annulus absent; limb orangish with maroon spots, 1-lobed, lobe ovate, 1-6 × 0.6 cm, pilose; gynostemium 5-lobed, crown-shaped, 1-4 mm; anthers 5; ovary 5-locular, to 1 cm. Capsule ovoid to obovoid, 1.5 × 1-2 cm, dehiscence acropetal; valves 5; septa entire, not attached to valves. Seeds flat, triangular, 0.3-0.4 × 0.4 mm.

Flowering spring-summer. Rocky slopes; 50-1000 m; Ariz., N.Mex.; Mexico.

Plant: Herbaceous perennial vine; woody taproot; stems prostrate

Leaves: linear-lanceolate to ovate, with cordate, sagittate, to hastate bases, puberulent, often purplish

INFLORESCENCE: axillary, solitary flowers

Flowers: pedunculate, with an ovate bracteole to 4 mm long; calyx tubular, brownish purple, zygomorphic, with 1 sepal lobe elongated, the mouth flaring; stamens 5; pistil 5-carpelled

Fruit: FRUITS cylindrical, dehiscent, valved capsules, 1.5-2.5 cm long, 1-1.5 cm wide. SEEDS black, triangular, ca. 4 mm wide, and long, numerous

Misc: Sandy roadsides and washes of open and canyon areas; 300-1450 m (1000-4800 ft); Mar-Dec

Notes: Flowers have a fetid odor.Leaves can be purple underneath.Seeds triangular in shape, black.Capsule septacidal.

References: Mason, Charles T., Jr. 1999. Aristolochiaceae. Ariz.-Nev. Acad. Sci. 32(1).

Duration: Perennial

Nativity: Native

Lifeform: Vine

General: Trailing perennial herb from a single, thickened, carrot-shaped root, the plant dying back to root in drought or with freeze. Stems slender, herbaceous, often less than 30 cm or vining to 1-1.5 m in shaded, moist habitats.

Leaves: Alternate and short-petiolate, the petioles 0.5 to 1 cm; blades to 12 cm long, triangular-hastate, the basal lobes as long as or longer than the petioles.

Flowers: Yellow to brown-purple, solitary in leaf axils; corolla is absent but calyx is showy, bilateral, tubular, and curved, yellow-green with brown-purple spots mostly along 5 prominent veins, margin and tip dark maroon.

Fruits: Capsule dehiscent, 5-valved, ovoid, 2 cm, with narrow ridge or wing along the midrib of each valve; seeds flattened, blackish, 0.4 mm.

Ecology: Found in gravely soils, along rocks in drier areas from 2,000-4,500 ft (610-1372 m); flowers July-September.

Distribution: AZ, s NM; south to n MEX.

Notes: This vining herb is easily identifiable by its dark green to maroon leaves with prominent central vein of light green and triangular-hastate shape. The flowers have a fetid odor and unique shape for insect pollination. Could be confused with a milkweed vine (Sarcostemma can have a similar leaf shape) but this species lacks milky sap and has much different flowers and fruits.

Ethnobotany: Used as a snakebite remedy, as a decoction it was medicinal for fever, and as a toxin for the removal of afterbirth (hence name birthwort).

Etymology: Aristolochia is from Greek, aristos, the best, most excellent and locheia or lochia, childbirth, hence name birthwort and watsonii for Sereno Watson (1826-1892) an assistant to Asa Gray.

Synonyms: Aristolochia porphyrophylla

Editor: SBuckley 2010, FSCoburn 2015, AHazelton 2015