Rhodiola integrifolia ssp. leedyi (Rosendahl & Moore) Kartesz
Sedum rosea var. leedyi, Sedum integrifolium ssp. leedyi, Sedum rosea var. integrifolium
Basis for Listing
Rhodiola integrifolia ssp. leedyi (Leedy’s roseroot) is an isolated subspecies of a more common western species (integrifolia) that is currently described as ranging from Siberia in Asia and from Alaska to California and New Mexico in North America. The two other subspecies (ssp. integrifolia and ssp. neomexicana) do not have geographic ranges that reach Minnesota or overlap with the range of subspecies leedyi (Moran 2009; Olfelt and Freyman 2014). John Leedy first discovered this subspecies in 1936 on a cliff along the North Branch of the Root River near Simpson, Minnesota in Olmsted County (Rosendahl and Moore 1947). Before then, it was unknown to science. Molecular and morphological studies show that this subspecies is very distinct from the other subspecies (Olfelt et al. 2001; Olfelt and Freyman 2014). There are seven known populations of subspecies leedyi known to be extant; four in Minnesota, two in New York, and one in South Dakota. Minnesota’s populations are restricted to two counties in The Blufflands. Estimates made in 2018 on Minnesota’s populations range from about 177 plants at the smallest site to about 596 plants at the largest site (Olfelt 2018). It is doubtful that additional populations will be found, because exhaustive Minnesota Biological Survey field searches have been conducted throughout most of the species suspected range in the state.
The primary factor limiting this species is the specialized cliff habitat it appears to require. Populations are also limited by their small size and their isolation. The federal recovery plan for R. integrifolia ssp. leedyi also recognizes the potential adverse effects of off-site influences, such as groundwater contamination and hydrologic alterations (U.S. Fish and Wildlife Service 1998). Because of these factors, R. integrifolia ssp. leedyi was listed as state endangered in 1984 and as federally threatened in 1992.
Recent observations by Olfelt (2018) have also identified a new threat to Minnesota’s populations related to climate change. At three sites, plants were observed below the cliff face in talus. It appears this is the result of storm damage from large scale precipitation events that have dislodged plants from the cliff face. Additionally, at one site a portion of the cliff has broken away and remains relatively unvegetated.
Rhodiola integrifolia ssp. leedyi is a very distinctive plant that cannot be easily mistaken for any other native Minnesota species. The stems and leaves are smooth and succulent, and the leaf margins are irregularly dentate to entire. The thick scaly rhizomes are prominent in the narrow rock crevices where the plants are rooted. It is dioecious, meaning the male flowers and female flowers are on separate plants. The flowers are red or yellow and occur in flat-topped clusters (cymes) (Clausen 1975).
The Minnesota populations of R. integrifolia ssp. leedyi are found on shallow ledges on north-facing dolomite cliffs up to 30 m (98 ft.) in height. Plants are restricted to crevices in maderate cliffs, a very specialized habitat of specific strata where groundwater seeps through the rock and is cooled by air coming from underground air passages in karst topography. This results in a constantly wet, dripping condition, an unusual product of a long geologic history.
In New York, this species occurs on cliffs along the western shore of Seneca Lake. And, similarly to the Minnesota populations, the one known population in South Dakota grows from rock fissures with seepage on a north-facing cliff.
Biology / Life History
Reproduction in R. integrifolia ssp. leedyi is usually sexually by seed and less often vegetatively by fragmentation of rhizomes (Olfelt et al. 1998). Flowers are insect-pollinated. Seeds at one New York site are reported to sometimes germinate in their follicles and produce seedlings on the parent plant (Clausen 1975). There is evidence from cultivation trials that plants may become sexually mature in their first or second season of growth (Olfelt et al. 1998).
Conservation / Management
The strategy for the conservation of R. integrifolia ssp. leedyi should involve a variety of actions, including conservation easements and acquisition of habitat. There is probably little that can be done to directly enhance protection of cliff-faces themselves, other than to prohibit rock climbing. But it is important to ensure that management practices on adjoining lands do not have an adverse effect on this species. Field and greenhouse studies suggest that the population on the only publicly owned site in Minnesota might be experiencing inbreeding depression or environmental stress. Two populations on privately owned land appear to be relatively stable (Olfelt et al. 1998; Olfelt 2018). Because individual populations are as genetically distinct from each other as the subspecies is from its western relatives, a redundant, formal protection strategy for R. integrifolia ssp. leedyi is appropriate.
Best Time to Search
The best time to search for Rhodiola integrifolia ssp. leedyi is from early May to late September, when identification is made easy by its thick succulent leaves.
Conservation Efforts in Minnesota
Biological understanding of this species exceeds conservation efforts. A publication entitled, Leedy's roseroot: a cliffside glacial relict (Sather 1993) was produced for the U.S. Fish and Wildlife Service. Also, a federal recovery plan was prepared that presents detailed actions necessary to secure the recovery of this species (U.S. Fish and Wildlife Service 1998). From 1997 to the present, the number of R. integrifolia ssp. leedyi individuals has been annually counted in most of the Minnesota populations. Sound estimates of population sizes and demographic characteristics are critical to developing intelligent management strategies for this species and should continue. This information enables us to predict the long-term viability of Minnesota populations.
The largest population in Minnesota is in public ownership allowing for directed conservation efforts. One example includes land managers exploring options to slow and prevent erosion from large scale precipitation events. Continued monitoring by Olfelt (2018) has seen this population persist through drought and higher temperatures in 2012. Preliminary viability estimates suggest that the population should persist in the near future, but it is not as secure as other populations found in Minnesota.
Derek S. Anderson and Welby R. Smith (MNDNR), 2020
(Note: all content ©MNDNR)
References and Additional Information
Clausen, R. T. 1975. Sedum of North America north of the Mexican Plateau. Cornell University Press, Ithaca, New York. 742 pp.
Moran, R. V. 2009. Rhodiola. Pages 164-167 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 8. Oxford University Press, New York, New York.
Olfelt, J. P. 1998. Population biology of Sedum integrifolium ssp. leedyi. Dissertation, University of Minnesota, Minneapolis, Minnesota. 63 pp.
Olfelt, J. P. 2013. Leedy's roseroot demographics summary 2013. Report submitted to the United States Fish and Wildlife Service, Region 3, Fort Snelling, Minnesota. 6 pp.
Olfelt, J. P. 2018. Leedy's roseroot status report. Report submitted to the Minnesota Department of Natural Resources, St. Paul, Minnesota. 7 pp.
Olfelt, J. P., and W. A. Freyman. 2014. Relationships of North American members of Rhodiola (Crassulaceae). Botany 92:901-910.
Olfelt, J. P., G. R. Furnier, and J. J. Luby. 1998. Reproduction and development of the endangered Sedum integrifolium ssp. leedyi (Crassulaceae). American Journal of Botany 85(3):346-351.
Olfelt, J. P., G. R. Furnier, and J. J. Luby. 2001. What data determine whether a plant taxon is distinct enough to merit legal protection? A case study of Sedum integrifolium (Crassulaceae). American Journal of Botany 88:401-410.
Rosendahl, C. O., and J. W. Moore. 1947. A new variety of Sedum rosea from southeastern Minnesota and additional notes on the flora of the region. Rhodora 49:197-202.
Sather, N. 1993. Leedy's Roseroot: a cliffside glacial relict. Minnesota Natural Heritage and Nongame Wildlife Program Biological Report 42. Minnesota Department of Natural Resources, in cooperation with the Office of Endangered Species, U.S. Fish and Wildlife Service, Twin Cities, Minnesota. 11 pp.
Smith, W. R. 1992. A report on the status of Sedum integrifolium ssp. leedyi (Leedy's roseroot) in Minnesota. Prepared for the United States Fish and Wildlife Service, Fort Snelling, Minnesota. 5 pp.
United States Fish and Wildlife Service. 1998. Sedum integrifolium ssp. leedyi (Leedy's roseroot) recovery plan. United States Fish and Wildlife Service, Region 3, Fort Snelling, Minnesota. vi + 31 pp.