This vine is a summer annual about 2-8' long that twines about
adjacent vegetation and branches occasionally. The slender stems are
light green to reddish green, terete, and covered with either appressed
white hairs (var. bracteata
or spreading tawny hairs (var. comosa
Alternate trifoliate leaves occur along these stems. The terminal
leaflets are up to 2½" long (var. bracteata
or as much as 4" long
the lateral leaflets are a little shorter. All leaflets
are ovate to ovate-rhombic in shape and smooth along their margins. The
upper surface of the leaflets is medium green and hairless to sparsely
covered with appressed hairs; the lower surface of the leaflets is pale
green and usually more hairy. In each trifoliate leaf, the petiolule
(basal stalklet) of the terminal leaflet is up to ¾" long, while the petiolules of
the lateral leaflets are about 1/8" long. The slender petioles are 2-6"
long. At the base of each petiole, there is a pair of small stipules
less than ¼" long. Occasionally, congested racemes of 2-15 flowers up
to 2" long are produced from the axils of the leaves. Individual
flowers consist of 5 petals, a tubular calyx with 4 teeth, several
stamens, and a pistil. The petals have a pea-like floral structure
consisting of an upright
banner, 2 lateral wings, and
a keel that is
curved upward. The edges of the banner are often folded backward, while
the narrow wings and keel project forward. The petals are light pink,
pale lavender, or white; the calyx is light green to nearly white and either hairless or hairy. The blooming period
occurs from mid-summer into the fall and lasts about 1½-3 months.
Fertile flowers are replaced by seedpods about 1-1½" long; these
seedpods are oblongoid and flattened with short curved beaks. Each
seedpod contains 1-4 relatively large seeds; individual seeds are
reniform and flattened. In addition to the preceding flowers and their
seedpods, Hog Peanut also produces self-fertile flowers that lack
petals. These inconspicuous flowers are produced on low stolons along
the ground; they mature into single-seeded fleshy fruits with an
obovoid shape. Sometimes, these fruits become subterranean.
The preference is full sun to light shade, moist conditions, and soil
containing sand or loam. The root system of Hog Peanut fixes nitrogen
in the soil through the assistance of symbiotic bacteria.
The native Hog Peanut is occasional
the two varieties of Hog Peanut, var. bracteata
and var. comosa
, are about equally common.
Habitats consist of floodplain woodlands, low wooded areas along
streams, soggy thickets, damp sandy meadows, and seeps. Some
disturbance is beneficial if it reduces the shade of canopy trees and
other kinds of woody vegetation.
caterpillars of Epargyreus
(Silver-Spotted Skipper) and
(Gold-Banded Skipper) feed on the foliage of Hog
Peanut. Other insect feeders include the aphid Microparsus variabilis
and several leaf beetles: Cerotoma
, and Sumitrosis
. Some of these beetles have larvae that
mine the leaves. Various vertebrate animals also use Hog Peanut as a
food source. Either the seeds or the fleshy fruits of
flowers are eaten by the Ruffed Grouse, Ring-Necked Pheasant, Bobwhite,
Passenger Pigeon (now extinct), White-Footed Mouse, and Meadow Vole;
the Ruffed Grouse also feeds on the foliage. To a limited extent,
White-Tailed Deer also feed on the foliage.
Near a stream in sandy
woodland at the
Indiana Dunes State Park in NW Indiana.
Sometimes the scientific name is spelled 'Amphicarpa
.' The common name refers to the fleshy fruits of
flowers, which are edible to humans. These unusual fruits distinguish
Hog Peanut from many other species in the Bean family. Another vine in
the Bean family, Apios
(Groundnut), produces edible
underground tubers. These tubers are part of the root system, rather
than a modified seedpod. Compared to Hog Peanut, Groundnut has compound
leaves with 5 leaflets and its flowers are often reddish brown and less
cylindrical in shape. Other vines in the Bean family have differently
shaped flowers and their leaflets are usually less broad and rhombic
than those of Hog Peanut.