Explore the Grounds

Limestone Habitat

Edgar T. Wherry, one of the Preserve’s founders in 1934, was also one of the country’s preeminent botanists. Between 1930 and 1955, he was a professor of botany at the University of Pennsylvania, where he had earlier earned a B.S. degree in chemistry and a Ph.D. in mineralogy. Armed with that rather unique background, he was passionate about exploring the special relationship between plants and their underlying geology.

Bowman’s Hill Wildflower Preserve afforded Wherry a unique opportunity to intensely pursue that interest, especially as it related to soil pH. During the Preserve’s early years, he experimented with a variety of habitat recreations by adjusting the soil substrate and pH. Wherry then planted those areas with assemblages of native plants similar to what he had observed in the wild.

You can still see vestiges of Wherry’s early work on the Preserve’s grounds today—most notably the limestone habitat located along the Fern Trail. The trail was designed by Wherry, who was also a fern specialist, in 1935. The purpose of the Fern Trail was to feature the great diversity of Pennsylvania’s native fern species. One of the challenges to his vision was that the underlying geology along the fern trail was magma-created diabase, which formed an acidic soil with a low pH. However, some of the ferns he wished to exhibit preferred a soil with a higher pH.

His solution? During the trail’s construction, he had several loads of coarse limestone rock trucked in and placed in a long, shallow pile along the uphill side of the pathway. As it slowly eroded over time, the basic chemical properties of the limestone raised the pH of the surrounding soil. Within this newly created habitat, Wherry was able to plant species of ferns and wildflowers that would have otherwise perished in the more acidic native soil.

Today, this limestone habitat is still home to several species of plants that cannot survive elsewhere on the Preserve. Most notable of these is the endangered and beautiful snow trillium (Trillium nivale), a diminutive wildflower that lives among the limestone rocks. It is the Preserve’s first spring ephemeral to bloom each year.