Amphicarpaea bracteata (L.) Fernald

Hog Peanut

Amphicarpaea bracteata plant2

Family - Fabaceae

Habit - Taprooted annual, climbing on other vegetation.

Stems - Twining, to 2 m, herbaceous, glabrous to densely pubescent with antrorse to spreading hairs.

Amphicarpaea bracteata stemStem.

Leaves - Alternate, pinnately trifoliolate, petiolate. Petiole to 5 cm long, hairy. Stipules ovate, membranous, to 5 mm long. Leaflets ovate to rhombic, variously pubescent, entire, to 10 cm long, usually bluntly pointed, often asymetrical at base, the stipels deciduous, 1-2 mm long. Stalk of center leaflet much longer than those of lateral leaflets.

Amphicarpaea bracteata leavesLeaves.

Amphicarpaea bracteata leaf2Leaflets abaxial.

Inflorescence - Pendant, axillary racemes.

Flowers - Chasmogamous flowers to 1.5 cm long, papilionaceous. Corolla purplish to white. Stamens diadelphous. Calyx of 5 sepals united more than half there length, upper two sepals united for entire length creating a 4-lobed calyx to 5 mm long.

Amphicarpaea bracteata flowersPurple flowers.

Amphicarpaea bracteata flowersWhite flowers.

Amphicarpaea bracteata calyxCalyx.

Fruits - (Of chasmogamous flowers) - To 4 cm long, flattened, with 2-4 seeds, oblong-linear. Fruits (of cleistogamous flowers) - 1 seeded, pyriform.

Flowering - August - October.

Habitat - Open woods, thickets, moist slopes.

Origin - Native to tropical America. Also cultivated.

Other info. - Steyermark listed two varieties for this species: var. comosa, having larger leaves and dense pubescence, and var. bracteata, having the opposing characters. Yatskievych did not formally accept this division, citing free intergradation, absence of geographical correlation, and frequent mixed populations. However, he also made note of some genetic basis for the distinction and stated the need for further work in the area.

Hog peanut has an interesting reproductive system. Open "chasmogamous" flowers, with papilionaceous corollas and normal pollination, are produced in short racemes from upper nodes. The fruits arising from these are flat legumes with 2-4 seeds each. On lower parts of the plant, "cleistogamous" flowers are often produced, sometimes even below the soil surface. These do not open and are self-pollinated. The fruits resulting from the cleistogamous flowers are large, fleshy, and one-seeded, and are an important food source for mice and voles. They were also gathered as a food source by Native Americans. When cooked they reportedly taste like green beans. This dichotomy is reflected in the genus name Apmphicarpaea, which means "two types of fruit."

Photographs taken in Brown Summit, NC., 9-8-02 (DETenaglia); also at Victoria Glade, Jefferson County, MO, 8-30-2015; and Little Lost Creek Conservation Area, Warren County, MO, 9-6-2016 (SRTurner).