American groundnut

not listed

N5? - Secure

SNR - Unranked

not listed

FAC - Facultative

FACW - Facultative wetland

FACW - Facultative wetland

American groundnut is a native climbing vine with attractive flowers and edible beans and tubers. It is native to the United States east of the Great Plains and to adjacent Canadian provinces. It is cultivated as an ornamental in Europe and as a food in Japan and possibly in South Korea. In Minnesota it is common in the southeast and metro regions, uncommon in the central and north-central regions, and mostly absent from the remainder of the state. It is found in bottomland forests and prairies, on banks of streams and rivers, in fens, marshes, fields, and gardens, on roadsides, and in disturbed areas. It grows in wet to moist areas under light shade to full sun in loamy, gravelly, or sandy soil.

American groundnut is a perennial vine that rises on multiple stems from a long, creeping, horizontal, underground stem (rhizome) and fibrous roots. Fleshy, thickened areas (tubers), modified for food storage, appear evenly spaced along the rhizome. The tubers are ¾″ to 2″ (2 to 5 cm) long and ⅜″ to ¾″ (1 to 2 cm) wide. It the tuber is separated from the plant it will produce another plant (clone). Plants often fail to produce seedpods, and reproduce mostly by cloning.

The stem is slender, round, light green and 3¼′ to 10′ (1 to 3 m) long. It is usually hairless or sparsely hairy, occasionally densely covered with short, fine, appressed hairs, rarely with longer hairs. It does not produce tendrils. It climbs by spiraling clockwise at the tip around the stem of an nearby plant (twining). When broken, the leaves and stem exude a milky sap.

The leaves are alternate and pinnately divided into usually 5 or 7 leaflets, sometimes just 3 leaflets. The leaf stalk (petiole) is slender and ⅝″ to 2¾″ (1.5 to 7.0 cm) long. It may be hairless or hairy. At the base of each petiole there is a pair of small appendages (stipules). Each stipule is ⅛″ to ¼″ (4 to 7 mm) long and hair-like.

The leaflets are ¾″ to 4″ (2 to 10 cm) long, and ¾″ to 2⅜″ (2 to 6 cm) wide. The leaf blades are egg-shaped or lance-shaped, rounded at the base, and angled or somewhat tapered to a sharp point at the tip. The upper surface is dark green, pinnately veined, and hairless. The lower surface is lighter green and hairless or sparsely to moderately covered with short hairs. The margins are untoothed. The terminal leaflet is on a ⅝″ to 13⁄16″ (15 to 30 mm) long leaflet stalk (petiolule) and is symmetric at the base. The lateral leaflets are on 1⁄16″to ⅛″ (2 to 3 mm) long petiolules and are symmetric or only slightly asymmetric at the base. At the base of each petiolule there is a pair of small appendages (stipels). Each stipel is 1⁄32″ to 1⁄16″ (1 to 2 mm) long and inconspicuous. The stipules and stipels are deciduous, dropping off early.

The inflorescence is an unbranched cluster (raceme) of several to many flowers rising from leaf axils. The raceme is ¾″ to 2″ (2 to 5 cm) long, often short, dense, and cone-shaped. It is on a hairy, ¾″ to 2″ (2 to 5 cm) long stalk (peduncle). At the base of the raceme there is a 1⁄16″ to ⅛″ (2 to 3 mm) long modified leaf (bract). At the base of each flower there is a 1⁄16″ to ⅛″ (2 to 3 mm) long secondary bract (bractlet). The bracts and bractlets are deciduous, dropping off early.

The flowers are about ½″ long. There are 5 outer floral leaves (sepals), 5 petals, 10 stamens, and 1 style. The sepals (collectively the calyx) may be light green or colored like the petals. They are united at the base into a broadly bell-shaped, 1⁄16″ to ⅛″ (2 to 3 mm) long tube then separated into one long and four short lobes. The long lobe is about half as long as the tube. The petals are brownish-red to brownish-purple. They form a butterfly-like corolla, as is typical of plants in the pea family. They are organized into a broad banner petal at the top, two narrow, lateral, wing petals, and between the wings two petals fused into a keel. The banner is strongly concave, broadly notched at the tip, and thickened at the top forming a small hood. The outer surface is usually pale or almost white. The wings are inversely egg-shaped, angled downward, and spreading. The keel is narrow, sickle-shaped, and strongly curved upward. The stamens are equal in length. The stalks (filaments) of nine of the stamens are fused together, the tenth is free. The style is stout and strongly curved or curled. It has a cap-like stigma at the tip.

The fruit is a 19⁄16″ to 2⅜″ (4 to 6 cm) long, 3⁄16″ to ¼″ (5 to 6 mm) wide seed pod with usually 4 to 6 seeds. It is somewhat flattened and is tapered at the tip. The seeds are dark brown, oblong to almost circular, ⅛″ to 3 ⁄16″ (4 to 5 mm) long, and ⅛″ (3.5 to 4.0 mm) wide. Fresh fruits are edible but only after being cooked.

Climbing: 3¼′ to 10′ (1 to 3 m) long

Brownish-red to brownish-purple

Wet to moist. Bottomland forests and prairies, banks of streams and rivers, fens, marshes, fields, gardens, roadsides, and disturbed areas. Light shade to full sun. Loamy, gravelly, or sandy soil.

July to August

Sources

2, 3, 4, 5, 7, 8, 24, 28, 29, 30.

Native

Common

Found growing on the shore of Gull Lake.

Vine

Flower

Stem

Leaf

Location: Albany, NY

Location: Fairview Twp, Cass County

Found growing on the shore of Gull Lake.