Vines annual or short-lived perennial, frequently mat-forming, with slender taproots. Stems trailing or climbing, to 250 cm. Leaves: stipules usu­ally ascending, ovate to broadly triangular, 1–2.5 × 0.8–2.4 mm; petiole 2–5.5 cm; rachis 0.5–2 cm; stipels linear to ovate-lanceolate, 0.5–1.5 mm; leaflet blades ovate in outline, not lobed or shallowly to deeply lobed basally, lobes quadrate-obtuse to oblong-attenuate, 1–5 × 1–4.5 cm, membranous to rigid, base broadly cuneate to truncate, apex obtuse to acute, surfaces covered with uncinate hairs, abaxially with incumbent hairs along veins. Peduncles often angled, 1–10 cm. Inflorescences 1.2–16 cm; axis covered with uncinate hairs; rachis 0.2–7.5 cm, with 2–6 biflorous nodes; primary bracts ovate to lanceolate, 1–2 × 0.5 mm, often pigmented, 3-veined. Pedicels 5 mm, hairs uncinate; bracteoles persistent, oblong-ovate to narrowly triangular, 0.6–1.3 mm, often covered with uncinate hairs. Flowers: calyx campanulate, 2–3.5 mm, sparsely to densely covered with uncinate hairs; abaxial and lateral lobes triangular; adaxial lobes connate; corolla pink, lavender, reddish to light purple, or white fading yellowish, 10 mm; banner oblong to orbiculate, 10 mm, apex emarginate, surfaces glabrous; wings obovate, 10 mm, apex acute or obtuse; keel 6 mm; ovary linear, 3 mm. Legumes pendent, compressed, linear-falcate, 23–35 × 4–5 mm, elastically dehiscent, valves membranous, sparsely covered with incumbent and uncinate hairs. Seeds 4–6(or 7), brown, usually oblong to quadrate, rarely reniform, 2–4.3 × 2.3–4 mm, rugose; hilum ovate, 0.3 mm. 2n = 22.

Phenology: Flowering year-round.
Habitat: Sandy, gypsum, limestone, or volcanic soils, juniper communities, open oak-pine forests.
Elevation: 0–1700 m.

Distribution

• Generated Map
• Legacy Map

Ariz., Calif., N.Mex., Tex., Mexico (Baja California, Baja California Sur, Chihuahua, Coahuila, Durango, Sonora).

Discussion

Phaseolus filiformis occurs from Riverside County, California, eastward through Arizona and New Mexico to western Texas (El Paso, Jeff Davis, and Presidio counties).

Phaseolus filiformis is easily distinguished by its slender taproot or fibrous root system, conspicuous variation in leaflet lobation, small number of flowers per inflorescence, falcate fruits, and seeds with rugose surfaces. In appearance, it is often confused with P. scabrellus, but the latter has a thick root system and smooth seeds.

Flowers, mature seeds, and immature pods are sometimes used as food (D. R. Newton 2013).

Selected References

None.

Lower Taxa

None.