Aureolaria pedicularia (L.) Raf.
Fernleaf False Foxglove
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Gerardia pedicularia, Agalinus pedicularia, Dasistoma pedicularia, Aureolaria pedicularia var. pedicularia, Aureolaria pedicularia var. ambigens
Basis for Listing
Aureolaria pedicularia is a plant of dry sand savannas in southeastern and east-central Minnesota. Three 19th century records of this species were the only documentation that it occurred in the state until an intensive survey was conducted between 1987 and 1995. During this survey, only three small colonies were found. This was far fewer than expected, leading experts to conclude that a significant decline in population had occurred. This conclusion is supported by a well-documented decline in suitable habitat. The major cause of decline is land conversion for urban and agricultural purposes. Habitat degradation, as a result of fire suppression and woody encroachment, also appears to be a limiting factor for this species. Aureolaria pedicularia was listed as a threatened species in Minnesota in 1996.
Aureolaria pedicularia has lacy, fern-like leaves 3-6 cm (1.2-2.4 in.) long. The stem may reach 1 m (39.4 in.) in height but is usually less than half that size. The flowers are relatively large, about 3 cm (1.2 in.) long, bell-shaped, yellow, and borne on the ends of long stalks. Stems are sticky and hairy.
Based on survey data in Minnesota, A. pedicularia seems to be restricted to dry, sand savanna or dry, open, oak woods with acidic soil. It exhibits a strong dependence upon oak trees, especially Quercus ellipsoidalis (northern pin oak) and Q. velutina (black oak).
Biology / Life History
Aureolaria pedicularia is a root parasite and depends almost entirely on oak trees for survival. In Minnesota, it shows a strong preference for Q. ellipsoidalis or Q. velutina. It is a biennial, and during its 1st year forms a rosette of leaves at the base of the plant. Its roots attach to the roots of other plants by the end of the 1st growing season. By June of the 2nd year, it sends up a flowering stalk. Some plants will flower into late autumn. Demonstrating the dependence of this species upon other plants, seedlings ceased to develop when removed from the host plant. However, mature plants separated from their host would still flower. The seeds require time under cold conditions in order to germinate (Musselman 1969, 1979; Werth and Riopel 1979).
Conservation / Management
Aureolaria pedicularia shows a strong dependence upon oaks for survival. Accordingly, a major threat is the loss of oak savanna habitat through conversion to agriculture, urbanization, succession to forest in the absence of fire, and invasion by non-native species. Livestock grazing, unregulated off-road vehicle use, and herbicides are other threats. Protection of the savanna ecosystem and maintenance of the oak component of these savannas is essential for conserving populations of A. pedicularia.
Conservation Efforts in Minnesota
Intensive surveys conducted by the DNR's Minnesota Biological Survey between 1987 and 1995 resulted in the discovery of three small colonies of A. pedicularia. One of these three may no longer exist, and all three populations contained 20 or fewer plants. Only one population, in the Whitewater Wildlife Management Area, is on public land. This population is monitored annually as part of a larger oak savanna restoration effort, and it appears to be responding positively to the introduction of prescribed fire. The population has grown from just one plant in the early 2000s to at least seven large plants as of 2008.
References and Additional Information
Musselman, L. J. 1969. Observations on the life history of Aureolaria grandiflora and Aureolaria pedicularia (Scrophulariaceae). American Midland Naturalist 82(1):307-311.
Musselman, L. J. 1979. A population of Aureolaria pedicularia (L.) Raf. (Scrophulariaceae) without oaks. American Midland Naturalist 102(1):175-177.
Werth, C. R., and J. L. Riopel. 1979. A study of the host range of Aureolaria pedicularia (L.) Raf. (Scrophulariaceae). American Midland Naturalist 102(2):300-306.