Prairie turnip
(Pediomelum esculentum)

2020 species of the year

Prairie turnip (Pediomelum esculentum).   Photo courtesy of John Zaborsky.

Keep your eyes peeled for the 2019 Species of the Year – Prairie turnip (Pediomelum esculentum). Each year the Rare Plant Monitoring Program picks a plant deserving special attention. Monitors are not required to survey for the species of the year, but the idea is to gain a statewide status update for a particular plant while also building excitement and allowing participants to become more familiar with one plant species

Species overview

The genus Pediomelum (from the Greek, for "apple of the plains") is endemic to North America, with about 29 species found across the continent,mostly west of the Mississippi River. Prairie turnip (Pediomelum esculentum) reaches its eastern limit here in Wisconsin but is common in the Great Plains and western Minnesota. The thick tuberous roots were an important part of the American Indian diet as well as for the European settlers who came later.

Prairie turnip photo

The leaves of prairie turnip are palmately compound with five leaflets.   Photo credit: Heidi Hankley

Habitat

Prairie turnip is found in dry and dry-mesic prairies in two disjunct regions in western Wisconsin: the Driftless Area south of the Wisconsin River and along the Kinnickinnic River in Pierce and St. Croix counties. It is only rarely found on the steep bluff prairies above the Mississippi River.

Prairie turnip pods

The flowers develop into hairy pods by July or August.   Photo credit: Heidi Hankley

Biology

Prairie turnip is a slow growing perennial that emerges in May and flowers shortly after through June. The plant is conspicuously hairy, particularly on the stems. The leaves are alternate and palmately compound with five leaflets. The inflorescence is composed of numerous bluish-purple stalkless flowers in a dense one- to three-inch spike. A one- to two-seeded pod develops in July and August.

Prairie turnip US range map

National distribution of prairie turnip. Taken from Biota of North America Program (BONAP).

Conservation Concerns

Like many other prairie dependent plants and animals,the main cause of prairie turnip's rarity is loss or degradation of habitat. Being at the eastern edge of its range, it was never common in Wisconsin, making it naturally more vulnerable than other prairie plants. In 1986, prairie turnip was listed as special concern,and since then almost 70 populations have been reported, including herbarium specimens. Of these, 25 are priorities for monitoring. Despite a relatively large number of prairie turnip populations in Wisconsin, very few are large and most have not been observed recently. Although a lot of prairie restoration has occurred in the last 30 years, prairies that have not received attention have likely degraded and the small prairie turnip populations that survived on these sites are particularly vulnerable to extirpation.

Prairie turnip photo

The stems and branches of prairie turnip are conspicuously hairy.   Photo credit: Robert Read

Identification tips

There aren't many plants that can be confused for prairie turnip in Wisconsin. The most closely related species, silvery scurf pea (P. argophyllum), is exceedingly rare and may only be represented here by a single population. Wild lupine (Lupinus perrenis) has palmately compound leaves like prairie turnip, but there are 7-11 leaflets instead of five for prairie turnip. Also,lupine has a much taller inflorescence of stalked flowers. Lupine is not nearly as copiously hairy as prairie turnip either. Wild indigos (Baptisia spp.) have a similar low bush-like appearance as prairie turnip but again,those species are not copiously hairy. They are also generally taller and have white to cream colored flowers.

Prairie turnip root tubers

The thickened root tubers give prairie turnip its name.   Photo credit: Bonnie Heidel

Prairie turnip range map

Prairie turnip range map.