Summer 1999

Mid-spring through fall best time to view plant blooms at St. Charles fen

Kane County, Illinois

Despite farmers' efforts in the early 1900s to drain and "improve" the wetland now known as Ferson Creek Fen in Kane County, the gem has survived. The 40-acre preserve, located in St. Charles along the Fox River, now is a dedicated Illinois Nature Preserve.

Water in a fen is very cold, contains a low level of oxygen, and has a very basic pH. "That provides unique conditions and certain plants have adapted to them, but others haven't," said Mary Ochsenschlager, natural resource manager for the St. Charles Park District, which owns the site.

Plant species such as Ontario aster, skunk cabbage, crested wood fern, bog lobelia, great St. John's wort, several rare types of goldenrod, and even wild rice can be found in the fen. Deer, coyote, and numerous species of water fowl call the fen home, along with mink, meadow jumping mice, and many kinds of frogs, such as the spring peeper. The blue gray gnatcatcher, prothonotary warbler, and yellow-throated vireo can also be seen hunting insects in the trees around the fen.

The fen itself occupies some 20 to 25 acres of the preserve; the remainder is upland prairie and sedge meadow. Imagine a fen as a soaked sponge floating in a shallow puddle. The sponge in this case is made up of a thick mat of partially decayed plant matter, or peat and muck. The puddle is supplied by water seeping up through the ground.

The plant matter doesn't fully decay because the water is so low in oxygen. A pinch of it examined closely reveals bits of leaves and stems. If two people stand on the mat and one jumps up and down, the other can feel it quaking, according to Ochsenschlager, hence the name 'quaking mat.'

Anytime from mid-spring through fall is a good time to visit Ferson Creek because there are always plants in bloom, Ochsenschlager said. "Wetlands and prairies don't have to wake up early to bloom," she added. "They can take their time because they don't have a tree canopy above them." She recommends visiting in the early morning or early evening for the same reason: the lack of shade makes for midday heat.

Interpretive signs along the boardwalk leading through the preserve describe the fen and how it works; provide information about the sedge meadow and flood plain forest; point out some of the unusual plant species; and describe the problems with invasive species. Probably the most pernicious of these is purple loosestrife, an imported garden ornamental. Herbicides are not used in the fen because of concern that the herbicide could spread to all of the plants via the water. So, staff and volunteers manually remove the plants. Beetles that feed on the loosestrife were introduced a few years ago, but positive results have yet to be seen, which is "pretty discouraging," Ochsenschlager said.

A slow paced walk through the fen takes less than an hour, Ochsenschlager said. She recommends visitors enjoy a stroll through the upland prairie where in the fall of 1997 workers and volunteers removed thousands of feet of drain tile and are now restoring natural prairie. Across the Fox River from Ferson Creek Fen is Norris Woods, another state nature preserve, profiled in the Spring 1999 issue.

For more information, contact the St. Charles Park District at (630) 513-3338.

— Benjamin Cox