Turn north 0.75 miles to the preserve entrance east of road. Silver Lake is one of many fens in northwest and northeast Iowa. Fens are water-saturated peat deposits fed by seeps where an underground aquifer discharges at the surface. Three of these upwellings are found at Silver Lake. The water is highly mineralized and deposits a mat of minerals, called tufa, on the water's surface and surrounding plant material.
Plant communities occur in distinct zones.
The discharge area is dominated by sedges, slough grass, and sawtooth sunflower. Moving downslope, the sedge mat zone is dominated by beakrush, arrowgrass, lobelia, and muhly grass. The border area of bulrush and sedge grades into a cattail marsh. Much of the vegetation occurs in spongy mats. These are easily damaged by foot traffic.