American Hog-peanut, Amphicarpaea bracteata

American hog-peanut climbing on purple coneflower.

American hog-peanut or hog peanut, Amphicarpaea bracteata, is a vining herbaceous annual plant in the pea family (Fabaceae) native to eastern North America from Manitoba east to Nova Scotia, south to Florida, west to Texas, and north to North Dakota and Montana. It is somewhat unusual because it produces two different types of flowers and seeds – and the genus name refers to that (Greek amphi (of both kinds) and carpos (fruit). The common name comes from the underground fruits, or “peanuts”, that are dug up and eaten by wild pigs.

American hog-peanut climbs by coiling stems.

It is found in moist woods, meadows and prairies but can invade similar types of ornamental landscapes. This plant is often considered a weed when growing in cultivated places. It is a larval host for silver-spotted skipper and northern cloudywing butterflies.

This plant grows from a seed, producing a twining, branched stem that can grow up to 5 feet long during the growing season from a slender tap root. Without tendrils, it climbs by coiling the apical portion of the stem around other plant stems.

Thin, twining stems (L) wrap around other plant stems (C) and may be smooth or hairy (R).

The alternate, trifoliate leaves are attached to the thin, smooth to very hairy stem on a long petiole with stipules at its base. The three broadly oval leaflets are often asymmetrical at the base and the petiolule of the center leaflet is much longer than those of the lateral leaflets. The leaves may turn gold or yellow in the fall.

A hog-peanut seedling (L and LC), eventually produces trifoliate leaves (RC) that often turn yellow in fall (R).

American hog-peanut produces two types of flowers. The flowers on the upper branches look like typical pea flowers, hanging in loose pendant clusters (racemes) from leaf axils in August and September. The flowers are about ½ inch long with four slightly asymmetric fused pale green sepals. The five elongate petals may be white, pale pink, lilac or pale purple. The flowers open before fertilization and are usually cross-pollinated (chasmogamy).

Hog-peanut flowering on brown-eyed Susan, Rudbeckia triloba (L), flower cluster hanging from stem (LC), closeup of flowers (RC,R).

The flowers are followed by flat, oblong spotted pods that are pointed at both ends and usually contain three or four seeds. The seeds are ballistically dispersed and can be cooked to be eaten and used in the same ways as lentils.

The seed pods (L) each contain 3 or 4 seeds (LC, RC) that are a mottled brown at maturity (R).

A germinated hog peanut, the fleshy pod produced by cleistogamous flowers.

The flowers that occur on the lower, lateral branches are inconspicuous, lack petals and do not open (the term for flowers that are self-fertilized without opening is cleistogamous). The ground level stolons search for crevices in the soil where they produce the flowers that rest on or under the ground. These are followed by a single-seeded fleshy pod that buries itself just below the soil surface in a manner similar to peanuts (Arachis hypogaea, although it is not closely related to that plant). These underground fruits are edible, and can be eaten raw or boiled to remove the hulls and the seed eaten like a nut. Many Native American people would they collect this “peanut” that can be up to ½ inch in diameter from the ground around the plant as a minor food source.

American hog-peanut can become a weed in shady gardens, here growing over Geranium sanguineum.

American hog-peanut grows well in most light conditions from full sun to full shade in moist soils of any type, and is typically found in and on the edge of woodlands, wet meadows and prairie, and in disturbed sites such as in gardens with dappled shade or along trails, roadsides and forest edges. It has occasionally been cultivated as a peanut substitute, but yields are rather low. Nodules formed by certain strains of Rhizobium bacteria on the roots fix atmospheric nitrogen which is utilized by the growing plant and by other plants growing nearby. To control where the plants are not wanted, pull repeatedly, several times a year for several years. Because they tend to be mixed in with other plants, chemicals may be difficult to use without damaging other plants unless all vegetation is to be removed.

– Susan Mahr, University of Wisconsin – Madison


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17 comments

  1. Did not know we had peanut plants in Wisconsin. Will have to try to find and identify this year.

  2. I am not sure if I have seen them in my area…but I will be watching.

  3. The American Hog-Peanut climbs by coiling the apical portion of the stem around other plant stems. I noticed in a picture that it wrapped itself around a purple coneflower. Does this affect the host plant in anyway causing the host plant not to be able to take in the necessary nutrition that it needs.

  4. Last summer a neighbor thought she had poison ivy in her back yard. You know it can be difficult to identify. We tried to ID the plant, sent some photos to the PHAs. Meanwhile another friend gave her a plant ID booklet and she suggested Hog Peanut. I brought a specimen into the PHAs, mentioned it might be Hog Peanut, and hurray, it was. The photos and descriptions in this Dec 2019 article will be very helpful if we find more in our neighborhood on the near-west side of Madison.

  5. Very interesting plant with the two types of flowers. Sounds like something I would not want to plant in my small city yard.

  6. Until I reached the last paragraph, I was thinking this might be used as a food source without a lot of input. The article says there is low yield of the ‘peanut’ during cultivation but did not mention if the seeds of the above ground pods are produced in enough abundance to be substantial food substitute for lentils

  7. My son and I have enjoyed harvesting the seeds. The underground ones were quite a bit larger than the ones that grow on the vines. We ate them but they were rather bland.

  8. It’s interesting that the plant has 2 types of flowers. The trifoliate leaves look a bit like poison ivy.

  9. Never knew we had a native peanut plant here in the U.S.! Will be on the lookout for them when I’m hiking.

  10. Very interesting article. Was not aware that we have these plants in our area that produce pods above and below ground. I will be looking for them and will give them a try.

  11. The petals in their white, pink, purple colors in the close up photos are rather pretty. Did not know we had such a plant in WI. Interesting article yes.

  12. Very interesting article….not sure whether I have them in my woods or not. Will be on the lookout. Just thought they are another weed of some sort. Did not know we have this native “peanut” in our area either.

  13. This is an interesting plant. I didn’t know we had a native type peanut in the US. I am wondering how being a host to the silver-spotted skipper and the northern cloudy-winged butterflies affects the plant? Do these insects have other plants that can support their life cycle?

  14. I’ve never found them to be a nuisance but will definitely be digging ip a peanut snack next time i see it!

  15. I thought this article was very interesting, especially that the pods are similar to peanuts.

  16. Quite interesting that flowers that do not open but can still be self-fertilizing (cleistogamous). So I definitely learned something there. I thought it was also interesting that this plant has both edible seeds from the pods above ground AND edible pods similar to peanuts that are underground. I’d be interested in tasting them, but maybe not interested enough to try and grow them myself.

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