Desmodium nudiflorum (L.) DC.
Stemless Tick Trefoil
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Basis for Listing
The mesic forest habitat of Desmodium nudiflorum (stemless tick trefoil) was widespread and extensive in the southeastern part of Minnesota at the time of settlement. However, agriculture and urban expansion have subsequently fragmented and isolated these forest habitats. Many surviving fragments have been degraded by grazing, logging, and invasive species. A serious effort has been undertaken to determine the floristic composition of these remnants, and to identify which species are rare and in need of special management consideration to survive. Desmodium nudiflorum is one of the species that falls into this category. It occurs in only a small percentage of surviving habitats, and even where it does occur, the number of individuals is generally low. On the basis of this information, D. nudiflorum was listed as special concern in Minnesota in 1996. Since that time, habitat trends have worsened. At the same time, invasion by non-native species has increased exponentially and has substantially reduced the amount of potential habitat. For this reason, the status of D. nudiflorum was elevated to threatened in 2013.
Desmodium nudiflorum gets its common name, stemless tick trefoil, from that fact that the flowering stem has no leaves. The leaves occur on a separate stem, about 50 cm (1.6 ft.) tall. They are compound, with 3 distinct leaflets, each 4-10 cm (1.6-3.9 in.) long. The flowers are pink to purple, 6-8 mm (0.2-0.3 in.) long, and arranged in a raceme or panicle. The fruit is a flat, segmented pod that separates into single-seeded segments that adhere to clothing or animal fur.
Desmodium nudiflorum occurs primarily in mature mesic oak forests. This habitat type is characteristically dominated by Quercus rubra (red oak) and Tilia americana (basswood), with lesser amounts of Q. alba (white oak) and Prunus serotina (black cherry). There are also a few records from drier forests, where Q. rubra would likely be replaced by Q. macrocarpa (bur oak) or Q. ellipsoidalis (northern pin oak).
Biology / Life History
Desmodium nudiflorum is a perennial, forest forb that occurs in small, localized colonies. It apparently does not become abundant enough to dominate a habitat, at least not in Minnesota. The flowers are small and inconspicuous, except to the flying insects that serve as pollinators. One study reported that adult plants of D. nudiflorum produce up to 109 flowers, with a mean of 50 flowers per plant (Schaal and Smith 1980). Twenty-two percent of the flowers produced fruit; each fruit contained an average of 2.8 seeds. Outcrossing is predominant in D. nudiflorum, with Bumblebees being the major pollinators. Asexual reproduction does not occur. The seeds are dispersed in pods that stick in the fur of mammals. The pods are held at a height of about 50 cm (1.6 ft.) above the ground, indicating that deer could be the primary dispersal agent.
Conservation / Management
There does not appear to be anything particularly unique in the biology or life history of D. nudiflorum that would require species-specific management. In other words, it is likely that conservation goals can be reached simply by maintaining its habitat in a natural condition. In most cases, this would require logging and livestock grazing to be excluded. In fact, healthy, full-functioning habitats need no management other than to be left alone. The only likely situation where active management would be required is in the case of exotic species invasion. Rhamnus cathartica (common buckthorn), Lonicera spp. (Eurasian honeysuckle shrubs), and Alliaria petiolaris (garlic mustard) are the most serious threats, however, it’s essential to monitor habitats for all invaders.
Best Time to Search
The best time to search for D. nudiflorum is when flowers or fruits are present, from early July through September.
Conservation Efforts in Minnesota
Desmodium nudiflorum occurs on at least four parcels that are owned by the MN DNR and managed for timber production. It also occurs at one site in a State Park. This population is probably secure, simply because most consumptive uses of natural resources are forbidden in state parks. The other sites, however, could be subjected to logging and other forestry-related management activities that could conflict with the conservation of this rare species.
Welby Smith, MN DNR, 1988, 2008, and 2017
Coffin, B., and L. Pfannmuller, editors. 1988. Minnesota's endangered flora and fauna. University of Minnesota Press, Minneapolis. 473 pp.
Isely, D. 1998. Native and naturalized Leguminosae (Fabaceae) of the United States. Brigham Young University Press, Provo, Utah. 1,007 pp.
Isely, D. I. 1955. The Leguminosae of the north-central United States II. Hedysareae. Iowa State College Journal of Science 30(1):33-118.
Minnesota Department of Natural Resources. 2005. Field guide to the native plant communities of Minnesota: the eastern broadleaf forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 394 pp.
Minnesota Department of Natural Resources. 2006. Tomorrow's habitat for the wild and rare: An action plan for Minnesota wildlife, comprehensive wildlife conservation strategy. Division of Ecological Services, Minnesota Department of Natural Resources. 297 pp. + appendices.
Minnesota Department of Natural Resources, Division of Ecological Resources. 2008. Rare species guide: an online encyclopedia of Minnesota's rare native plants and animals [Web Application]. Minnesota Department of Natural Resources, St. Paul, Minnesota. Accessed 1 July 2009.
Minnesota Department of Natural Resources, Division of Fish and Wildlife. 1995. Statement of need and reasonableness in the matter of proposed amendment of Minnesota Rules, Chapter 6134: endangered and threatened species. Minnesota Department of Natural Resources, St. Paul, Minnesota. 336 pp.
Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis, Minnesota. 320 pp.
Schaal, B. A., and W. G. Smith. 1980 . The apportionment of genetic variation within and among populations of Desmodium nudiflorum. Evolution 34(2)214-221.