Phaseolus parvulus is a viney pea with solitary or nearly solitary pink-purple flowers and lanceolate, trifoliate dark green leaves. There is a small, globose bulb just under the soil surface. Phaseolus parvulus is found in the understory of the upper elevation Ponderosa Pine Forest.

Kearney and Peebles 1969, McDougall 1973

Duration: Perennial Nativity: Native Lifeform: Vine General: Erect, slightly twining stems arising from a deep-seated, globose tuber, to 30 cm long, with bracts at the base of the pedicel only, not subtending the inflorescence. Leaves: Trifoliate, lanceolate leaflets, leaflets entire, to 1 cm wide or less, dark green above and lighter in color beneath, with a prominent midvein, glabrous or nearly so. Flowers: Purple, keels somewhat contorted, corollas 15-20 mm long; 1-2 flowers per peduncle in axillary racemes. Fruits: Flat, linear pods 2.5-3.5 cm long, glabrous to slightly pubescent, with 2-3 seeds. Ecology: Found in rich soils in coniferous forests from 6,500-8,000 ft (1829-2438 m); flowering August-September. Notes: The most obvious key to this species is the large, globose taproot; if you don't want to dig the plant up however, look to the mostly erect stems, the bracts which subtend the peduncle only and the pods 2.5-3.5 cm long. The pods are completely dehiscent, the two halves curling in a spiral. The seeds are round and somewhat large, as with all Phaseolus. Samples of this species show a highly variable leaf morphology, with some leaves becoming somewhat large and broadening in the middle with age. Ethnobotany: There is no specific use of this species recorded, but the seeds of the genus were used extensively as a food source. Synonyms: Alepidocalyx parvulus Editor: LCrumbacher, 2011 Etymology: Phaseolus comes from the Greek phaselos, "a little boat or light vessel," referring to its similarity to a bean pod, this name became the Latin phaseolus used for a kind of bean, while angustissimus means very narrow.