Rare Species Guide

  Synonyms

Aureolaria pedicularia var. pedicularia, Agalinis pedicularia, Aureolaria pedicularia var. ambigens, Dasistoma pedicularia, Gerardia pedicularia

  Basis for Listing

Aureolaria pedicularia (fernleaf false foxglove) is a plant of dry sand savannas in east-central and southeastern Minnesota (St. Paul-Baldwin Plains and Moraines, Anoka Sand Plain, Big Woods, and The Blufflands subsections). It is endemic to temperate regions of eastern North America and the Great Lakes states. Three 19th century records of this species were the only documentation that it occurred in the state until an extensive survey was conducted between 1987 and 1995. During that survey, none of the previously known populations were located, but three small previously unknown colonies were found. This was far fewer than expected. For that reason experts concluded 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.

  Description

Aureolaria pedicularia is a tall bushy plant, sometimes reaching 1 m (39 in.) in height but is usually less than half that size. It is easily recognized by its lacy, fern-like leaves 3-6 cm (1.2-2.4 in.) long. The bright yellow flowers are relatively large, about 3 cm (1.2 in.) long, bell-shaped, and borne on the ends of long stalks. The stems are sticky and hairy. There is no similar-looking plant species in Minnesota.

  Habitat

Based on survey data in Minnesota, A. pedicularia seems to be restricted to dry sand savanna and dry, open, oak woods with acidic soil. It exhibits a strong dependence on oak trees, especially Quercus ellipsoidalis (northern pin oak) and Q. velutina (black oak). Soils are coarse-textured, well-drained mineral soil, usually with a very low organic content. Light intensity is variable.

  Biology / Life History

Aureolaria pedicularia is a root parasite and depends almost entirely on the roots of oak trees for survival. In Minnesota, it shows a strong preference for Q. ellipsoidalis or Q. velutina. Research has shown that seedlings ceased to develop when removed from the host plant. However, mature plants separated from their host continue to develop and produce flowers (Werth and Riopel 1979). Aureolaria pedicularia is often reported to be a biennial, but it seems to function as an annual in Minnesota, completing its entire life cycle in one year. The flowers are pollinated by a large number of non-specialized bee species (Grundel et al. 2011).

The only population currently known to be extant in Minnesota is monitored annually as part of a larger oak savanna restoration effort. Monitoring has revealed that the population fluctuates wildly from year to year, which is typical for annual species. There may be as few as 50 individuals or as many as a few hundred. Monitoring to date has not revealed any obvious correlation between population fluctuations and weather or fire. However, it is believed that fire is essential for the long-tern maintenance of the habitat in which the plants live. The variability in numbers is believed to be the result of variable recruitment from a seed bank in the soil. It is assumed that a certain percentage of viable seeds in the soil will germinate in response to environmental variables that are not yet understood. It is known that the seeds require time under cold conditions in order to germinate (Musselman 1969, 1979; Werth and Riopel 1979), but it is likely that additional stimuli are needed. The population under study is believed to be viable in the long term as long as the habitat is maintained in a natural condition.

  Conservation / Management

Aureolaria pedicularia shows a strong dependence upon oaks for survival. Accordingly, a major cause of past decline is the well-documented loss of oak savanna habitat through conversion to agriculture, urbanization, succession to forest in the absence of fire, and invasion by non-native plant species. Livestock grazing, unregulated off-road vehicle use, and herbicides are present threats to the integrity of surviving habitats. Perhaps paradoxically, the disease of oak wilt, which is fatal to most oaks, can help maintain the open aspect of savannas and reverse some of the problems caused by historic fire suppression. Protection of the savanna ecosystem and maintenance of the oak component of these savannas is essential for conserving populations of A. pedicularia.

  Best Time to Search

The best time to search for Aureolaria pedicularia is when flowering, from August through September.

  Conservation Efforts in Minnesota

Extensive surveys conducted by the Minnesota Biological Survey between 1987 and 1995 resulted in the discovery of three small colonies of A. pedicularia. Two of these three may no longer exist. Only one population, in the Whitewater Wildlife Management Area, is on public land and receives any management.

  Authors/Revisions

Welby R. Smith (MNDNR), 2021

(Note: all content ©MNDNR)

  References and Additional Information

Grundel, R., R. P. Jean, K. J. Frohnapple, J. Gibbs, G. A. Glowacki, and N. B. Pavlovic. 2011. A survey of bees (Hymenoptera: Apoidea) of the Indiana Dunes and northwest Indiana, USA. Journal of the Kansas Entomological Society 84(2):105-138.

Morawetz, J. J. 2019. Aureolaria. Pages 555-559 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 17. Oxford University Press, New York, New York.

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.