Rare plant found in Wisconsin after not being seen since 1911

Wisconsin DNR volunteer George Riggin and Habitat Biologist Bridget Rathman with the rediscovered Maryland senna plant (Photo Courtesy: Wisconsin DNR).

A population of the rare plant known as Maryland Senna (Senna marilandica) was rediscovered by a Wisconsin DNR volunteer along with a habitat biologist in the southwest part of the state after not being seen for more than 100 years, state officials say. 

That volunteer, George Riggin, was trained as a part of the Wisconsin DNR’s Rare Plant Monitoring Program. Riggin, along with DNR Habitat Biologist Bridget Rathman, spotted the plant in 2023. 

The Rare Plant Monitoring Program’s 2023 Annual Report states the discovery comes after a five-year search that saw George following leads across Wisconsin. He credits the help of other plant specialists and his "stubborn streak" for finding the elusive specimen. 

The report also explains how to tell the difference between northern wild senna and Maryland senna, the main characteristic of which is the presence of seed pods. 

The plant was previously thought to be observed in Wisconsin back in the 1970s, but was found to be misidentified. The last confirmed sighting of the plant was in 1911 and then 1883 before that. 

DNR officials say more than 50 trained volunteers in Wisconsin submitted 178 reports of rare plants, including 31 populations of rare plants in areas of Wisconsin where they had not been documented before. The DNR adds that almost 15% of Wisconsin’s 2,366 native plant species are considered rare, which means they are listed as endangered, threatened or of special concern. 

George also shared advice for novice plant monitors.

"A person needs to start simple, find a plant that chooses you, a plant that for whatever reason, you have an interest in," he said. "It's also fun for me. If it wouldn't have been for having new leads, I might have given up."  

Tips and opportunities on how to be a volunteer plant monitor can be found here.