Jeffersonia diphylla (L.) Pers.
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Basis for Listing
Jeffersonia diphylla reaches the northwestern edge of its geographic range in the forests of southern Minnesota. The forests were vast when settlers first arrived, but have since been largely supplanted by farm fields. All that is left today are small, isolated remnants in deep stream valleys where agriculture is impractical. Only a small number of these remnants are known to support viable populations of J. diphylla.
Jeffersonia diphylla is a spring flowering perennial forb that may reach about knee high. There is no above-ground stem, instead the leaves and the flower stalks grow directly from an underground rhizome. The flower stalk is 10-20 cm (3.9-7.9 in.) high and has a single white flower. The flower is relatively large (up to 4 cm (1.6 in.)) and has 8 petals and 8 stamens. The leaves are somewhat shorter than the flower stalk in the spring, but each leaf petiole continues to lengthen into summer and may eventually reach 30-40 cm (11.8-15.7 in.). Each leaf blade is 8-15 cm (3.1-5.9 in.) across and is divided into 2 equal-sized segments. It is these paired leaf-segments that give the plant its name "twin-leaf", and provide a fool-proof means of identification. The flower looks something like the flower of Sanguinaria canadensis (bloodroot), a common associate that flowers a week or two before J. diphylla, but the leaf of S. canadensis is not divided.
Jeffersonia diphylla occurs in mesic hardwood forests, specifically southern mesic maple-basswood forests (Minnesota Department of Natural Resources 2005). These forests are characterized by a continuous and dense canopy of deciduous trees, primarily Acer saccharum (sugar maple), Tilia americana (basswood), and Quercus rubra (northern red oak). These are quite stable, late successional communities with historic catastrophic windstorm intervals of over 650 years. Catastrophic wildfires were even more uncommon with a historic return interval of over 1,000 years in the bluff country where J. diphylla is found. The variety and abundance of forbs within these forest communities is severely limited by the deep shade. The rooting zone of the soil consists of moist loam with a substantial organic component. This type of forest has developed at several places in southern Minnesota, but only those that are found in the stream-dissected Blufflands of the southeastern counties harbor J. diphylla. Within these forests, J. diphylla tends to occur on north-facing slopes where conditions are cooler and moister.
Biology / Life History
Jeffersonia diphylla is a perennial forb that flowers in early spring. It is not considered a spring ephemeral because the leaves remain intact and photosynthetically active all summer. They usually remain green until the first killing frost in October. Individual flowers remain open for 2-6 days and the entire flowering period lasts about 10-14 days (Smith et al. 1986). The flowers produce no nectar, but they do produce copious pollen, which attracts pollinators, primarily bees. If cross-pollination is not successful, autogamy (self-pollination) may occur (Smith et al. 1986).
Conservation / Management
In Minnesota, J. diphylla typically occurs in stable, late successional forest communities that are able to perpetuate themselves without major disturbance or intervention. From a management perspective this means the forest can and, in most cases, should be left alone. Forest management practices that open gaps in the canopy or disturb the soil, and livestock grazing should be avoided. Hunting, maple syrup harvesting, nature study, and other low-impact uses will probably cause no harm as long as motorized vehicles are not used.
Conservation Efforts in Minnesota
Jeffersonia diphylla is known to occur in a number of protected habitats, including two State Parks.
Baskin, J. M., and C. C. Baskin. 1989. Seed germination ecophysiology of Jeffersonia diphylla, a perennial herb of mesic deciduous forests. American Journal of Botany 76(7):1073-1080.
Heithaus, E. R. 1981. Seed predation by rodents on three ant-dispersed plants. Ecology 62(1):136-145.
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.
Rockwood, L. L., and M. B. Lobstein. 1994. The effects of experimental defoliation on reproduction in four species of herbaceous perennials from northern Virginia. Castanea 59(1):41-50.
Smith, B. H., M. L. Ronsheim, and K. R. Swartz. 1986. Reproductive ecology of Jeffersonia diphylla (Berberidaceae). American Journal of Botany 73(10):1416-1426.