The Driftless Area of southwestern Wisconsin contains a plethora of native plants across its diverse habitats. Some plants have gone extinct. Others are stalwarts, adaptable to change. Some continue to exist albeit battered by the rigors put on them by a changing world. The prairie turnip (Pediomelum esculentum) is among the latter, a floristic oddity as a western plains plant sustaining here — out of place.
Prairie turnips’ homeboys are found in the Plains, the Dakotas and the Flint Hills of Kansas. Here is the most eastern location the plant can be found. A Dane County specimen is likely the most eastern in the country. It is found in dry prairies, especially on hillsides with limestone and/or near oak woodlands. In Wisconsin, it is primarily found only in the five-county region of southwestern Wisconsin.
Under ideal conditions it is abundant in the Plains states. Palatable and nutritious, it was once a staple food used by Native Americans as well as by early Europeans. It was harvested May through July when the flower stalks were easily visible. The root was harvested with a sharpened digging stick. The tubers have a hard, dark skin and are peeled before eating. Some were eaten immediately, either raw or boiled, but most were dried for further use. They were sliced and sun dried, braided and hung on meat racks to dry, and pounded into flour. It was reliable in times of shortage or famine. It is nutritious, high in protein, carbohydrates, vitamins and minerals. Particularly important was the vitamin C content. The prairie turnip takes two to four years to grow from seed to mature root. The long period required for maturation probably limited the success of any efforts made to cultivate the plant. Descriptions of its taste range from a “delicacy” to “tolerably good eating” and “tasteless and insipid.”
Like other rare prairie species, the primary cause of prairie turnip’s scarcity is habitat loss. Located at the eastern edge of its range here, it has always been susceptible. In 1986, it was listed as a plant of ‘special concern’ in Wisconsin.
There has been an increase in renaming plants by taxonomists recently. This plant has also fallen to academia’s proactivity. It was formerly psoralea esculenta. Botanists prefer the uniform Latin nomenclature as it decreases confusion in regional and national settings. Common names for this plant include prairie potato, breadroot, tipsin, teepsenee and pomme de prairie among others. Wisconsin botanists today use prairie turnip.
Prairie turnip is a slow-growing perennial that emerges in May and flowers through July. The plant is obviously hairy, particularly on the stems. The leaves are alternate, ascending the stem in a spiral, and palmately compound, radiating in a hand-like configuration with five leaflets. The inflorescence is composed of numerous blues to purple stalkless flowers in a condensed spike. A one- or two-seeded pod develops in July and August. Like people, plants also have preferred associations. The prairie turnip can be found hanging out with white oak, black oak, little bluestem, the gramma grasses, silky aster and other typical dry prairie species. Here in the Driftless, it is always found on well-drained slopes mostly with a sandy element and usually facing west or south.
Like other rare prairie species, the primary cause of prairie turnip’s scarcity is habitat loss. Located at the eastern edge of its range here, it has always been susceptible. In 1986, it was listed as a plant of “special concern” in Wisconsin. Only 70 populations have been reported, including herbarium specimens from the past. Despite these numbers, very few populations are large, and several have not been observed recently. Prairie remnants that have not received management have likely degraded and the already declining prairie turnip specimens on these sites are particularly vulnerable to extinction. Mesophication from expanding tree growth, lack of fire and increased rainfall are the pronounced pressures. Its need for well-drained dry soil creates an unfavorable situation in an era of increasing annual precipitation — mainly in the form of increasing heavy rainfall events that inundate soils with excessive moisture unable to drain. The plant serves as a canary-in-the-coal mine indicator from the pressures brought on by these increased rainfall events.
This plant can serve as a regional mascot of sorts as we attempt to recognize and battle atmospheric and landscape changes in the Driftless. This plant is distinct, living in this area, and will regress under subtle changes. We have the ability to care for the prairie turnip by raising awareness of the issues that burden it, and we can provide the support that it cannot give itself. If all goes well, we will always be able to enjoy its annual blooms as will the many species that use it. In the meantime, pediomelum esculentum can be monitored as an indicator to how things are going in general.
Cory Ritterbusch is a restoration ecologist, historian and writer. He consults through his business Prairie Works, works for the Southwest Wisconsin Regional Planning Commission and is the executive director of Advance Shullsburg Inc.