Pitcher plants nestled in amongst sphagnum moss. Photo by IDNR.

May 1, 2023

Bogs Host Unique Plants, Hearken to the Last Glacier in Illinois

Some of the harshest living conditions for plants in Illinois can be found in bogs. That’s where unique flora such as the carnivorous pitcher plant grows, along with tamarack, a conifer that loses its needles in winter after they turn yellow in the fall, and sphagnum moss, which was used in ancient times to preserve butter.

A blue map of the state of Illinois with the top right section in white. To the top right of the map is a zoomed in section that shows the white area larger and in more detail.
Volo bog is located in the Northeast Morianal Natural Division. Illustration by Sarah Marjanovic.

“These plants grow where others cannot,” said Stacy Iwanicki.

Iwanicki, a Natural Resources Coordinator for the Illinois Department of Natural Resources, oversees educational programs at Moraine Hills State Park, in McHenry County, which contains Leatherleaf Bog, and Volo Bog State Natural Area in Lake County, the only open water bog in the state.

“At Volo Bog, there’s an amazing biodiversity of vegetation,” Iwanicki said. “You can find pitcher plants, six species of ferns, including cinnamon fern, seven species of willows, and bog buckbean and starflower, which bloom in spring. So many of these plants are near the southern extent of their range.” They have adapted to the acidic condition of the bog, which offers few nutrients to plants and contains low oxygen levels.

Bogs, like other wetlands in the region, are products of glaciers. When the last glacier was retreating north from what is now Illinois, ice began to break off in huge chunks. As the climate warmed the ice melted and lakes formed. The lake in which Volo Bog would eventually form was left by the glaciers about 10,000 years ago. Other lakes had inlets and outlets, in which water could flow. But bogs have no outside water source, which causes poor drainage, stagnant water and the formation of a thick, floating mat of sphagnum moss and other plants, which can grow dense enough to support the state-endangered tamarack tree.

Bogs in the United States are mostly found in the northeast and Great Lakes, many of them also connected to glacial action. In New England and Wisconsin, bogs serve as a habitat for growing cranberries.

A flowering plant blooms small clusters of white flowers at the top of a green stalk at the edge of a wetland.
Bog buckbean flowering on the edge of the bog. Photo by Steve Bailey.

Bogs in Illinois grow within the Northeastern Morainal Natural Division of the state.

“There are roughly 12 bogs in this region, most of which are protected,” Iwanicki said. Some include Cranberry Slough, a peat bog in Cook County; Barrington Bog, a grassy bog in Lake County; Leatherleaf Bog at Moraine Hills State Park in McHenry County; and Volo Bog in Lake County, which was dedicated as an Illinois Nature Preserve in 1970 and registered as a National Natural Landmark in 1973. There are other smaller bogs that are inaccessible. Barrington Bog is being restored by Citizens for Conservation. Volunteers work to remove invasive exotic species, such as buckthorn, purple loosestrife and giant reed, which harm the bog regime and its native plants such as large cranberry and bog willow.

Volo Bog is the most accessible and offers the closest connection to this rare habitat.

“At Volo Bog you can see sphagnum moss up close and personal and touch a tamarack tree to feel how soft the needles are,” Iwanicki said.

In the natural world, bogs and fens may transition into other ecosystems over time. The other bogs in Illinois are further along in succession than Volo Bog.
“But the transition is slow,” she said. “There are a lot of factors that can affect what ultimately happens with a bog.”

She noted that over the years, scientists have discovered one small inlet attached to Volo Bog. Some are calling it a fen. Iwanicki prefers to label it as a bog-fen.

“Volo Bog presents a unique opportunity to view the entire vegetal encroachment in a bog that has been developing since the melting of the last continental glaciers,” wrote Murray R. McComas, John P. Kempton and Kenneth C. Hinkley in a 1972 publication of the Illinois Geological survey titled, “Geology, Soils, and Hydrogeology of Volo Bog and Vicinity.”

Zones of a bog that can be explored at Volo include the eye of the bog, reached by walking a boardwalk to the open water center. Surrounding the open water center is an herbaceous mat made of sedges and grasses.

The low shrub zone is farther away from the bog center and it’s where you’ll see leatherleaf, blueberry, small willows and sphagnum moss.

“The roots of the shrubs hold everything together and the sphagnum causes them to float,” Iwanicki explained.

Some rare plants in the low shrub zone include pitcher plant and bog buckbean and young tamarack trees.

“Bog buckbean is one of the most unique and intriguing flowers you’ll ever see because it has fringes on its petals,” Iwanicki said.

Beyond the low shrub zone, the floating mat of sphagnum moss gets thicker and can support large plants like tamaracks. Beyond that zone is the tall shrub zone where you can see poison sumac and winterberry holly. The bright red berries of the holly persist in winter, contrasting with the white snow blanketing the landscape. They also attract fruit-eating birds such as cedar waxwings.

The farthest zone from the eye is a marsh moat.

“The marsh zone looks familiar to anybody who drives by wetlands in eastern Illinois,” she said. “But the marsh zone around Volo Bog is healthier than the average marsh in Illinois. It’s got a lot of diversity.”

“Bogs are incredibly important to preserve,” Iwanicki said. “The bogs sequester 10,000 years or so of carbon.” Release that carbon and it will contribute to global warming. In Europe, peatlands, containing sphagnum moss have been drained for centuries to harvest the decaying layers of dead plants (called peat) for various uses including soil amendment in gardens. “We really need to halt the mining of ecologically valuable peat beds,” Iwanicki said.

Sheryl DeVore writes environment and nature pieces for regional and national publications and has had several books published, including “Birds of Illinois” co-authored with her husband, Steven D. Bailey.

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