Lake in the Hills Fen Nature Preserve provides nearly 400 acres of unspoiled native Illinois landscape. There is over a mile of maintained trails wendind through three diverse habitats: dry hill prairie, sedge meadow, and a rare and beautiful fen.
You can join them for a guided tour at 2:00 p.m. on the third Sunday in May and the second Sunday of each month from June through October. Meet near the parking lot in Barbara Key Park for up to a 90 minute walk over a mile of maintained trails. Please be prepared for full sun and occasional mosquitoes.
Visit and learn about fens and seeps. Large gravel deposits left by the glaciers allow rain water to percolate down until it reaches a less permeable layer, usually clay. Choosing the path of least resistance, the water travels horizontally, absorbing minerals and alkalinity from the gravel. Within the preserve are several places where the clay layer is exposed and the water is able to "seep" out. Unlike single-source springs, seep water exits the ground all along the line of the exposed clay. When the exposed clay layer lies up a hillside or near the top of a hill, the emerging water from the seep runs downhill. These geological features are called "hanging fens," designating a wetland on a slope. Lake-in-the-Hills has nine seep locations and eight of them include hanging fens. There are only 26 acres of hanging fens in the nation and Lake-in-the-Hills has approximately four of them. Among the rare biological communities found at this site are graminoid fen, calcareous floating mat, low shrub fen, calcareous seep, dry gravel prairie, and sedge marsh.
Nine distinct native communities occur here and include calcareous floating mat, graminoid fen, low shrub fen, calcareous seep, sedge meadows and marsh, perennial stream, dry gravel prairie and mesic gravel prairie.
Fen water is alkaline (unlike a bog, which has acidic water) and is heavily laden with minerals. The water stays a constant 50°F, having traveled through the ground, so it continues to flow year-round. Not surprisingly, this rare geological ecosystem harbors many of the site’s 16 threatened and endangered plant species such as the false asphodel. The fen is also home to the state’s smallest dragonfly, the tiny bluebell, found at only one other site in Illinois.
Lake-in-the-Hills also harbors prairies and gravel hills. On the south side of the preserve, you’ll see a berm-like hill known as an "esker." Its north and south exposures harbor many special plants such as Hills’ thistle, prairie smoke, prairie gentian, and leadplant.
Lake-in-the-Hills Fen is open year-round during daylight hours. There are 1.25 miles of mown trails, and guided nature walks are conducted at 2 p.m. the second Sunday of the month (May — October). Don’t miss the observation deck on an adjacent hillside, outfitted with a descriptive plaque and telescope by local benefactor, Joan Larsen.
Many rare plants are found in the fen including the false asphodel. The fen is home to the tiny blue bell, our smallest damsel fly, which is known to exist in only two sites in Illinois. Associated with the fen is the shrub fen, dominated by shrubby cinquefoil. Closer to the stream, sedge meadows provide a rich habitat for many uncommon wetland butterflies and birds as well as a variety of sedges, grasses and forbs. The sedge meadows grade into cattail marshes which border the perennial stream. From the center of the preserve, surrounded by the gravel hills and overlooking the lush green vegetation of the wetlands, it is possible to get a sense of stepping back in time.
To arrange a guided walk for private groups, including for hearing- or visually-impaired, call stewards Alan and Barbara Wilson at (847) 658-0024 or the McHenry County Conservation District (815) 678-4431.
Location:
Algonquin Township (T43N,R8E) Sections 17,20,21
Size: 450 acres
Natural Resources
Communities
Dry gravel prairie (C)
Sedge meadow (A,B,C)
Graminoid fen (A,B,C)
Calcareous seep (A,B)
Calcareous floating mat (A)
Streamside marsh (C)
Rare Plants:
Asclepias lanuginosa/Woolly milkweed (E)
Carex cryptolepis/Small yellow sedge (E)
Carex viridula/Sedge (E)
Eleocharis pauciflora/Few-flowered spike rush (E)
Scirpus cespitosus/Tufted bulrush (E)
Triglochin maritima/Common bog arrow grass (E)
Triglochin palustris/Slender bog arrow grass (E)
Utricularia cornuta/Horned bladderwort (E)
Valeriana uliginosa/Bog valerian (E)
Carex crawei/Crawe’s sedge (T)
Cirsium hillii/Hill’s thistle (T)
Eleocharis rostellata/Beaked spike rush (T)
Galium labradoricum/Bog bedstraw (T)
Ranunculus rhomboideus/Prairie buttercup (T)
Rhynchospora alba/White beak rush (T)
Tofieldia glutinosa/False asphodel (T)
Rare Animals:
Aflexia rubranura/Redveined prairie leaf hopper (T)
Emydoidea blandingii/Blanding’s turtle (FED-SC,T)
Dolichonyx oryzivorus/Bobolink (W-SC)
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