With slender, branching, twining stems that can reach 4–12 feet long and with fibrous roots, this plant has been a valuable food and medicinal source in the Southwest for thousands on years. The highly drought-tolerant plant yields small high-protein, high-fiber beans. Note the palmately compound leaves with 3 leaflets, the pink pea-like flowers with a coiled keel in the center, and the slender pods with 5–10 small beans.

FLOWER: August–October, triggered by summer monsoon rains. Pink, purple to whitish flowers, 3/8 inch long (1 cm) in loose clusters of 2–5, usually blooming one at a time. Pea-like with one upper banner petal, two side or wing petals, and a distinctively twisted, whitish-green central keel of 2 petals. The calyx (sepals) cupping the flower base has 5 lobes or teeth. Note that Tepary bean pods are 1 1/4–2 3/4 inches long (3–7 cm) with 5–10 seeds (not 3–4).

LEAVES: Alternate, palmate with 3 leaflets, each 1 1/4–2 1/2 inches long (3–7 cm). Phaseolus acutifolius was previously divided into two varieties based on leaflet shape: var. acutifolius has 3 triangular, broad-based leaflets that taper to a slender-tip, blade 1 1/2–2 times longer than wide; var. tenuifolius has 3 narrow leaflets 2–10 times longer than wide, often with a small lobe on one or both sides of the base.

HABITAT: Sandy, gravelly, loamy soils; brushy, rocky slopes, stream sides, ravines; desert grasslands and scrub; pinyon-juniper, pine-oak woodlands.

ELEVATION: 4,600–6,700 feet.

RANGE: AZ, NM, Trans-Pecos TX.

SIMILAR SPECIES: Easily confused with the Slimleaf Bean, P. angustissimus, a perennial in much the same range and habitat with a woody taproot, bean pods 3/4–1 1/4 inches long (2–3 cm), and with only 3–4 seeds (not 5–10). Long-leaf Cologania, Cologania angustifolia, in conifer forest habitats in much the same range, has 3 narrow leaflets but not a coiled keel.

NM COUNTIES: Western half of NM in low-elevation, dry habitats: Bernalillo, Catron, Dona Ana, Grant, Hidalgo, Luna, McKinley, Rio Arriba, Sierra, Socorro, Valencia.