Lora Conrad lives on a small farm in Van Buren County.

The American Hog Peanut is also called American Wild Peanut. Amphicarpaea bracteata is a vining annual plant in the Pea family (Fabaceae). It can also be a short lived perennial. It is somewhat unusual for a legume in that it thrives in shady areas.

Amphicarpaea is reported to mean either “two kinds of flowers” or “two kinds of fruit,” both of which it has. Bracteata means “with bracts” at the base of the flower, which show clearly in the flower photos. It is the only Amphicarpaea sp. native to eastern North America and to the west, throughout Iowa. This BONAP map shows its Iowa and nearby distribution.

Preferred Conditions. It thrives in moist areas but can tolerate drier areas. It prefers sandy or loam soil. Open woods with moist slopes are its favorite terrain, which it has found in Van Buren County above a stream. It has created a dense mat of vines with heavy blossom and pod set. I saw a patch in September in the Hunt Woods Recreation area near West Burlington. There the ground was very dry. There were no blooms or pods on those vines.

The Leaves. When the seedlings come up in early May, they will not look like the leaves of the mature plant. At that point, they are just a pair of oval leaves. You are likely to begin to notice them in late spring when you will see “leaves of three” which Iowans have been conditioned to associate with poison ivy. There are many leaves of three and more each time you go by them on a trail as the vine grows. But, no, not the least bit poisonous.

Notice that these leaves of three are smooth edged, the center one symmetrical and triangular, the other two unsymmetrical. They are alternate on the stem. In the fall, they will turn yellow. The first photo shows the front of a leaf; the second, the back of that same leaf.

The Hog Peanut vines. At first, Hog Peanuts appear low-growing, but by summer, they begin to vine. The vines are host to silver-spotted skipper, gold-banded skipper, and northern cloudy wing butterfly caterpillars.

Usually there will be numerous plants in an area. By early August, they will have covered everything around. They can easily cover an acre of ground and all the other plants less that six feet high in that area. This is an early August photo showing that more leaves are growing and it is already covering other woodland plants, including Coralberry and Multiflora Rose.

As a vine, Hog Peanut can overwhelm surrounding plants. It does not use twisting tendrils as do so many vines, but wraps itself around whatever is in its path. This includes the invasive Multiflora Rose as shown below. The plant has one lead vine from which several other long thin vines with leaves will form. The entire vine can grow to 5 or 6 feet in length as it winds around whatever is in its path. The stem is either light green or reddish.

The next photo shows how it has wrapped itself around a quite large, healthy Multiflora Rose stem.

By blossom time, the foliage is thick and pretty near impenetrable.

I dug several plants searching for a nut. (No, I did not take a mirror. Think about it.) As you can see the plants are shallow rooted, with fibrous roots that divide into even finer roots. But the tangle of vines makes them difficult to dig.

By the end of August, the tangle of vines is formidable. They will be at least six feet high if the undergrowth has plants high enough for them to grow over.

This Great Blue Lobelia somehow managed to keep its bloom stalk above the Hog Peanut vines.

Blossoms and Seed. By mid- to late August. the Hog Peanuts will also be blooming. The blooms that form on the upper nodes of the plant are beautiful. They are hanging in loose, pendant clusters. Most are purple and white. Insects pollinate these flowers.

Here you can see the long bract hugging the base of each flower.

Some are pure white as shown below. These flowers are lying over the leaves of a Coralberry, which is producing berries despite being swamped by the Hog Peanuts.

Seed pods begin to form in mid-August. The pods are produced quickly from the blossoms. The next photo shows an open blossom, forming pods with the dried blossom still covering and pods large enough to see the seed forming, all on the same stem. The pods are produced quite prolifically.

A snail seems to appreciate the pods in the next photo. Note the hairy edge on the pod which is a key characteristic of the Hog Peanut pods.

Each pod may have up to four seeds that will begin maturing by mid-September. If you do not pick, shell and eat them (yes, they are edible), these pods will split open when dry to disperse the seed. According to the Illinois Wildflowers website, Ruffed Grouse, Ring-Necked Pheasant, Bobwhite, White-Footed Mouse, and Meadow Vole all feed on the seeds.

The photo below shows both a green seed pod opened and a ripe seed pod opened, both with seeds removed. For size, compare the peas to the foot of an average size cat (Kitty Velcroe) that was just about to take a swipe at them. The yellowing pods are not easy to open, so it would take a very long time to pick and shell enough for a meal!

More Blossoms and Seed. I mentioned earlier that this plant produces two kinds of flowers and two kinds of seeds produced. That is a most unusual method of reproduction. The discussion above presented the method of flower and seed reproduction with which we are most familiar, chasmogamous flowers—flowers blooming on the plant, open and visible, being pollinated. The resulting fruit is hanging on the plant or in pods on a vine.

But this plant can also have cleistogamous flowers that are often but not always produced. These do not require pollination for seed set and often do not even open. In the Hog Peanut, these flowers can be on the ground or even sometimes below the surface of the soil—meaning they are also geocarpic plants. Each flower of this kind produces a single seed (bean or nut shaped) in the soil.

The common peanut has a similar system, though those flowers always bloom above ground then grow down into the ground to make the nut. That similarity, and the fact that both humans and animals can eat Hog Peanut nuts, accounts for the use of the word “peanut” in its name. Indigenous people and struggling settlers would eat these nuts in areas where plants produced them. Hogs, both wild and domesticated, are much more efficient at harvesting these than people and often fed upon them in the woodlands. That may be why they were called Hog Peanuts.

For the same reason (productivity without harvesting the tuber), in the late 1800’s, hogs were sometimes fed on common peanuts and sweet potatoes. Farmers planted these and saved labor by allowing hogs to harvest them for food.

Despite the many Hog Peanut vines in Van Buren County, and the many seed pods hanging from the vines above ground, after digging several vines, and finding nary an underground tuber, I can not show a photo of them. This photo shows the detail of the root system, and clearly no seed growing.

Several articles reported that they are “finicky” producers, at best—that is, not a reliable producer of food in this way. However, when they do produce these underground bean shaped “nuts,” the nuts are eagerly eaten by mice, rats and voles. If you find some, they will first look like a clod of dirt. When you remove the outer hull, there will be one speckled seed or nut there. People who have eaten them report different tastes—some say they taste rather like green beans; others say they taste similar to peanuts. There is a photo of the underground “peanut” near the end of this article at Friends of Eloise Butler Wildflower Garden.

Conclusion. Hog Peanuts, while native, are not likely to be something you would want in a garden or anywhere there is restricted space. You would never want to try to run through a patch! But where they can grow unrestrained, they improve the soil, provide ground cover in wooded damp areas, provide beauty, sometimes provide food for people and especially provide food and cover for many kinds of native wildlife including deer, rabbits, mice, voles and numerous insects.

Resources. The following are excellent resources for greater detail about the Hog Peanut. They were among the resources consulted in writing this blog.

An article at Missouri Plants with superb photos, even of plant details.

A scientific discussion about it, with identification details at Friends of Eloise Butler.

A thorough article in the Illinois Wildflowers database to assist identification.