Water is the foundation
A sustained groundwater supply keeps the rooting zone wet. The area feeding that water can extend beyond the visible wetland.
Hidden groundwater. Extraordinary life.
A fen can look like a meadow, but the water beneath it tells a different story. Follow the springs, sedges and wildflowers into one of our most fascinating wetlands.
Fens receive water that has travelled through mineral soil or rock. In a calcareous fen, that water carries dissolved calcium and other minerals. It can seep quietly through the soil without forming a visible spring.
On a small screen, swipe across the diagram to read every label.
A sustained groundwater supply keeps the rooting zone wet. The area feeding that water can extend beyond the visible wetland.
Calcium-rich water can create alkaline conditions while nitrogen and phosphorus remain scarce. Those demanding conditions help shape an unusual plant community.
Unexpected fact: some fens occur on gentle slopes or raised peat mounds. A wetland does not always sit in the lowest hollow.
A peat-forming wetland influenced by water that has contacted mineral ground. Fens range from weakly acidic to alkaline; not every fen is calcareous.
A peatland whose plant-rooting zone receives most of its water from rain and snow. Bogs are generally acidic and nutrient-poor. Explore bogs.
A wetland dominated by soft-stemmed plants, often with shallow standing water. Marshes may receive both surface water and groundwater; peat formation is not their defining feature.
A preserve may include a fen, marsh, lake edge, meadow and woodland. Its name does not mean every photograph taken there shows fen habitat.
This page emphasizes the calcareous and prairie-fen landscapes of our Wisconsin and Illinois visits. Across the Great Lakes region, other fen communities have different plants and water chemistry.
Calcium-bearing groundwater supports sedges, flowering plants and low shrubs. Some sites have pale marl deposits; others look like lush meadows.
Mineral-influenced peatlands can support sedges, brown mosses and scattered shrubs. “Rich” describes their mineral influence, not a promise of fertile garden soil.
Weaker mineral influence creates more acidic conditions. Sphagnum mosses and some plants also associated with bogs may occur.
Seeps, low sedge lawns, raised tussocks and shrubby edges create different growing conditions only a few steps apart. No single layout fits every site.
Before tall summer growth fills the view, notice fresh sedge shoots and the shapes of hummocks. Look from established trails for early flowers and returning birds.
Flowering plants draw insects. Pause beside a bloom and watch who arrives, how they land, and which part of the flower they visit.
Gentians, goldenrods, Grass-of-Parnassus and lady’s-tresses can reward a later visit. Bloom timing varies by species, site and weather.
Seed heads, low shrubs and old stems reveal the framework of the meadow. Groundwater may keep some seep areas unfrozen, even when nearby ground is icy.
Try a repeat visit: photograph the same view from the same trail in spring, summer and fall. Which plants become visible, and which disappear behind taller neighbors?
Sedges and other grasslike plants form much of the living structure. The flowers below add seasonal color, while ferns and shrubs create shelter. These are photographs from fen preserves and their surrounding wetland habitats, not a checklist for every fen.
Look closely: the green veins in Grass-of-Parnassus petals; the tiny flowers arranged along a lady’s-tresses spike; and the difference between a fern frond and a grasslike leaf. Use your camera’s zoom instead of stepping into the vegetation.
A fen connects with neighboring grassland, shrubs, woodland and open water. These animals were photographed in those preserve landscapes. Some are visitors or edge species, rather than fen specialists.
1 Rain soaks in · 2 Water moves through soil · 3 Groundwater feeds the fen
Simplified pathway, not to scale.
Drainage, pumping and changes to the surrounding land can alter the water supply. A fen’s conservation boundary may need to include its groundwater recharge area.
Vegetation can slow runoff and trap sediment. Dissolved nutrients are not visible, and buffers do not remove every pollutant.
Extra fertilizer or eroded soil can favor vigorous plants over fen specialists. Mineral-rich groundwater is not the same as polluted runoff.
Land managers may control invasive plants, remove encroaching brush or use carefully planned fire. Management must fit the site and its sensitive species.
Stay on designated trails and boardwalks, leave flowers and mosses in place, and follow preserve rules. Soft peat and small plants can be damaged by a single shortcut.
Peat is a slow-built archive: waterlogged conditions slow decay, allowing plant remains and carbon to accumulate. Drying the peat can speed decomposition and change the habitat.
Follow our photographs of spring-fed channels, wetland flowers and the surrounding lake landscape.
Explore an Illinois preserve where fen, prairie and neighboring habitats form a varied landscape.
See the fen route and overlook within Retzer Nature Center’s larger landscape.
Our Lake in the Hills Fen, Clover Valley Fen and Ferson Creek Fen pages offer more photographs and visitor-information links.
Check each preserve’s official visitor information before going. Trails and access vary, and sensitive areas may be closed.
Field photographs: Where’s Wildlife. Artwork and diagrams are teaching aids, not site surveys.