Indiana University botanists record first appearance of wildflower species in Indiana

Environmental change may be responsible for first observation of giant blue cohosh in state

Indiana University botanists, in collaboration with local wildlife enthusiasts, recently recorded the first known presence of a wildflower in the state: Caulophyllum giganteum, commonly known as giant blue cohosh.

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The first confirmed sighting in Indiana of the wildflower giant blue cohosh as collected by IU botanist Daniel Layton in Martin State Forest. Daniel Layton

Members of the IU Herbarium confirmed the presence of the species in Indiana following an earlier sighting of the plant. The discovery was reported in the spring 2018 issue of the INPAWS Journal of the Indiana Native Plant and Wildflower Society.

"This discovery, now confirmed in two Indiana counties, raises interesting questions," said Eric Knox, IU senior scientist and director of the IU Herbarium. "Was this species simply overlooked during the past 110 years, or has Caulophyllum giganteum recently colonized Indiana in response to the changing climate?"

The giant blue cohosh is similar to the common blue cohosh, Caulophyllum thalictroides, another species familiar to spring wildflower enthusiasts in Indiana. Unlike the common blue cohosh, however, the giant blue cohosh is larger and blooms earlier in the season.

Previously, the plant was thought to be restricted to the northeastern United States and southeastern Canada.

The first evidence of the plant's presence in Indiana came in spring 2017 after state resident Kimberly Miser and her mother, Susie Watson, spotted the flower while hiking in Steuben County's Robb Hidden Canyon, which borders Michigan and Ohio. The hikers reported the plant to Michael Homoya, a botanist at the Indiana Department of Natural Resources. INPAWS member Kate Sanders helped collect photographs and measurements of the plant.

But the plant's presence in Indiana was not positively confirmed until last month, after IU botanist Daniel Layton came upon the plant in Martin State Forest in southwestern Indiana's Martin County on April 6. A member of the IU Herbarium, Layton holds a collection permit from the Indiana Department of Natural Resources. Knox said that photographs and field measurements provide preliminary evidence, but physical specimens are the gold standard of botanical research because the details can be examined microscopically.

Confirmation of the discovery was conducted by Paul Rothrock, associate curator at the IU Herbarium, who compared the specimen with the herbarium's 68 specimens of common blue cohosh, 58 of which are from Indiana, as well as other relevant published literature.

"We took a cautious approach to confirmation since we had not seen this species for Indiana and because the Martin County site was remarkably distant from known populations in Kentucky and Ohio," Rothrock said. "However, after collection of several more specimens and photos upon a return trip to the site, we can confidently identify this flower as Caulophyllum giganteum."

Layton added that he nearly didn't recognize the plant since the appearance of giant blue cohosh is remarkably different from the common variety.

"Common blue cohosh normally has yellow flowers that appear after the leaves are fully open; this plant had deep maroon flowers blooming before its strange gray-black leaves had fully unfurled," he said. "The discovery of Caulophyllum giganteum in Indiana is really something special."

Knox said the discovery highlights the fact that Indiana's natural resources are not completely known, and that citizen scientists -- along with professional botanists -- have important contributions to make in monitoring the state's native flora and fauna and preparing for the impact of environmental change.

Established in 1885, the IU Herbarium contains about 155,000 plant specimens, including the personal collection of Charles Deam, the first state forester for the state of Indiana and author of the book "Flora of Indiana" in 1940. A complete list of wildflowers in the state of Indiana is documented on the Consortium of Midwest Herbaria website.