Three rare and valuable natural features of the preserve include Wagner Fen, Flint Creek and wooded bluffs. Oak woodlands surround the fen and creek, providing habitat for songbirds, woodpeckers and hawks.
Wagner Fen: In 2001, the 55-acre Wagner Fen portion of Grassy Lake owned by the Lake County Forest Preserves was dedicated as an Illinois Nature Preserve, in conjunction with the 45 acres previously dedicated by Barrington-based Citizens for Conservation (CFC). Combined, the Wagner Fen nature preserve complex totals 100 acres. The fen is co-owned by CFC and the Village of Tower Lakes.
An ecologically-valuable wetland, the fen is home to eight endangered and threatened species. CFC and Forest Preserve natural resource crews worked together to successfully preserve and restore Wagner Fen. A biological control project designed to eliminate the non-native purple loosestrife from the fen has resulted in almost complete eradication of the evasive plant species from the site.
Flint Creek: One of the healthier streams in Lake County and in the state of Illinois, Flint Creek's quality rating of a Grade B is considered rare for Illinois. With help from an Illinois Environmental Protection Agency grant, stream banks along the Flint Creek corridor were restored.