Points of Interest:
• Look out across the largest fen – a unique wetland – in the Ozarks.
• See plants and animals that are ice-age relicts.
• Enjoy the hum and flights of dragonflies and damselflies across the wetlands in summer.
Natural History: Grasshopper Hollow contains the largest known fen complex in unglaciated North America. Fens are wetlands created when calcareous groundwater seeps out to the soil surface and are typically dominated by herbaceous plants kept open by both saturated soils and historically occasional wildfires. These fens are created by groundwater moving down through the Gasconade dolomite formation and hitting a resistant layer, likely sandstone, along which the water then runs horizontally and seeps out onto the lower slopes along the valley. Water that feeds these fens originates in the immediate 2,000 acre surface watershed but also from losing streams in the Logan Creek valley to the south, demonstrating the complexity of water movement in karst landscapes.
Fens at this site range from areas of shallow (up to 15 inches deep) muck soils dominated by sedges, ferns and wildflowers to deep (up to 40 inches deep) muck soils with pools of standing water and hummocks of sedges. An unusual prairie fen also occurs here and is dominated by a mix of prairie and fen plants growing in seasonally saturated soils. Eight plant and five animal species of conservation concern are found in these fens, including the Hine’s emerald dragonfly, a fen-restricted species of the midwest, that is listed as endangered by the U.S. Fish and Wildlife Service.
Many of Grasshopper Hollow’s rare species are considered “glacial relicts.” That is, they are species that were common in Missouri 10,000 years ago when glaciers covered the upper midwest. In the intervening thousands of years Missouri’s climate has gotten warmer and drier. The glacial relict species were able to persist in fens and along spring branches where cool groundwater provides appropriate habitat conditions. Other glacial relict species in Missouri persist on cool, moist north facing bluffs. At Grasshopper Hollow’s fens, glacial relicts include the four-toed salamander, wood frog, Riddell’s goldenrod, marsh blue violet, interior sedge, tussock sedge, sweet William phlox, and marsh bellflower. The combination of tallgrass prairie plants such as big bluestem and prairie cordgrass growing in association with characteristic fen plants such as orange coneflower and interior sedge is botanically interesting.
This wetland oasis is unusual in the otherwise dry and rocky Ozark landscape. Historically many Ozark valleys in the Black River basin supported fens. Because these areas were the best sites for settlers to crop and intensively graze livestock most fens have been destroyed or seriously degraded. Today The Nature Conservancy and the Mark Twain National Forest are using prescribed fire and watershed protection efforts to conserve the biological resource at Grasshopper Hollow.
From the junction of Highway A and Highway 72 in Bunker, travel east on Highway 72 approximately 7.6 miles to Forest Service road 860. Forest Service road 860 is 1.0 mile past the intersection of Highway 72 and Highway TT. Turn left (north) on 860 and travel 0.6 miles to the parking lot and trailhead. Visitors can walk the trail that follows an old road to view the fens. Note that walking in the fens themselves is not recommended as it can cause quite a bit of trampling damage and one can get stuck in muck over three feet deep. The Karkaghne Section of the Ozark Trail (see http://www.ozarktrail.com or call 573-436-0540) crosses the upper end of Grasshopper Hollow between Highway TT and Sutton Bluff campground (Mark Twain National Forest). Hunting is allowed on the Mark Twain National Forest portion of the natural area.