Delisting of Running Buffalo Clover

By: Heidi Braunreiter, Office of Kentucky Nature Preserves Plant Ecologist 

Running Buffalo Clover (Trifolium stoloniferum) is a perennial clover with showy white flowers and leaves divided into three leaflets, and was historically native to several eastern and midwestern U.S. states. Based on numerous references to clovers in historical literature, it is believed to have been abundant across its historical range in pre-settlement times, which included the Bluegrass Region of Kentucky (Campbell et al. 1988). However by 1900, its extent had drastically reduced, and only five populations in total remained (Brooks, 1983). Throughout the 20th century, there were numerous fruitless attempts to relocate populations, which lead scientists to believe the species was extirpated from states where it was historically common. Finally, in 1983 populations were relocated in West Virginia and Indiana, as well as in northern Kentucky in 1987 (Campbell et al. 1988). With so few populations known, the U.S. Fish and Wildlife Service (USFWS) opted to list the species in 1987 as ‘federally endangered,’ because it was at a high risk of extinction (USWFS 2007).

The decline of running buffalo clover is believed to have been caused by a combination of factors: as land was settled, habitat destruction ensued and competition from non-native invasive species became a problem (Campbell et al. 1988). Another factor was the loss of the American Bison on the landscape. Historical observations noted the clover’s preference for sites where American Bison congregated (Bartgis 1985). Bison likely provided a means of fertilizer, seed scarification, seed dispersal, and the periodic disturbance regime necessary for the running buffalo clover’s life cycle (Campbell et al. 1988). The loss of bison from the landscape would have dramatically affected the species’ propagation.

Today, you will find running buffalo clover in areas that have periodical disturbances mimicking bison; for example, along trails where plants get trampled, in old estate lawns or cemeteries that are regularly mowed, and on stream terraces with occasional flooding events. Running buffalo clover also prefers dappled sunlight in a forested setting. If the forest canopy becomes either too closed or too open, running buffalo clover populations tend to decline in number as it does not tolerate full shade or full sun (USFWS 2021).

Over the past two decades, the Office of Kentucky Nature Preserves (OKNP) has conducted monitoring on running buffalo clover populations in Kentucky in order to look at population trends and manage for non-native invasive plants. Over this time, many new county records were discovered through targeted searches of historical estates, cemeteries, and stream restoration efforts in the Bluegrass Region. Several successful propagation and introductions efforts have also occurred over the years, for example, new populations were introduced and are now self-sufficient at Shaker Village at Pleasant Hill in Mercer County and Taylor Fork Ecological Area in Madison County.

In 2019, running buffalo clover was proposed for delisting by the USFWS, as many populations had been discovered since its initial listing over 30 years prior. In response to the 2019 proposed delisting, OKNP conducted a state-wide assessment of our running buffalo clover populations. Despite set-backs from the pandemic, we were able to survey 61 populations, which covered the majority of the known extant populations in Kentucky. Sites not included in the assessment were already determined to be extirpated, or inaccessible. Most populations in Kentucky occur on private lands, and although obtaining access to private lands can be difficult, we have been grateful for the curiosity, interest, and enthusiastic response from many property owners. Overall, population trends in Kentucky show approximately half of the populations as stable or increasing in size while the other half of populations are declining in size or extirpated (Table 1). Figure 1 shows an updated range map of extant running buffalo clover populations in Kentucky.

Table 1. Population trends of running buffalo clover in Kentucky during the 2019-2020 statewide survey. 

A huge success that came out of the 2019-2020 statewide survey was the discovery of the largest running buffalo clover population in Kentucky. On the Mt. Folly Farm in Clark County, a population of over 6,000 plants was counted along the Upper Howards Creek. Other large populations of running buffalo clover in the state top out around 1,000 to 2,000 plants. The significance of this population led to the creation of a new Registered Natural Area with OKNP at Mt. Folly Farm. The clover occurs in the floodplain of the creek in cattle pastures and riparian woods. This site holds potential for future research as it has running buffalo clover in areas with and without a cattle-grazing regime.

As of September 2021, running buffalo clover was delisted by USFWS as they believe there are a sufficient number of populations occurring on publicly owned and managed lands to sustain the species’ viability (USWFS 2021). As of 2020, 175 extant populations occur across its range in Indiana, Kentucky, Missouri, Ohio, Pennsylvania and West Virginia, and biologists in these states discover new populations every year. Within Kentucky, many populations occur on Wildlife Management Areas where stream restoration projects are ongoing. The key to the future success of this plant is the continued management of populations to keep invasive plants at bay and the continued implementation of appropriate disturbance regimes, be that mowing, grazing, or trampling.

If you are interested in adopting a running buffalo clover population in Kentucky to do yearly checkups to remove invasive species, please contact me! heidi.braunreiter@ky.gov.  

Figure 1. Extant range of running buffalo clover in Kentucky as of February 2021. 

Bibliography 

Bartgis, R. 1985. Rediscovery of Trifolium stoloniferum Muhl. ex A. Eaton. Rhodora 87:425–429. 

Brooks, R. 1983. Trifolium stoloniferum, Running buffalo clover: Description, distribution, and current status. Rhodora 85:343–354. 

Campbell, J.J.N., M. Evans, M.E. Medley, and N.L. Taylor. 1988. Buffalo clovers in Kentucky (Trifolium stoloniferum and Trifolium reflexum) – Historical records, presettlement environment, rediscovery, endangered status, cultivation and chromosome number. Rhodora 90:399–418. 

USFWS. 2007. U.S. Fish & Wildlife Service: Running Buffalo Clover (Trifolium stoloniferum) Recovery Plan: First Revision. Department of the Interior, U. S. Fish and Wildlife Service, Great Lakes-Big Rivers Region (Region 3), Fort Snelling, MN. 

USFWS. 2021. U.S. Fish & Wildlife Service. Running Buffalo Clover Final Listing Determination Fact Sheet. https://www.fws.gov/midwest/endangered/plants/rbcl/runningb.html. Accessed 2 September 2021.