The Michigan Road preserve is a valuable piece of the Port Huron area’s natural history. It’s a fascinating complex of forested swamp and upland sand ridges bordering an almost impenetrable shrub swamp. The forest is largely a second-growth northern community composed of northern species like Red Maple, Paper Birch, Black Ash, Blueberry, Wintergreen, Bunchberry, Bracken Fern, Wild Sarsaparilla, Starflower, and Canada Mayflower. Michigan Endangered Painted Trillium is known from nearby locations with similar northern forest habitat and is likely on the preserve. Interior portions of the preserve are covered by northern shrub swamp dominated by dense thickets of Tag Alder, Black Chokeberry, and Nannyberry, mixed with invasive Glossy Buckthorn and Common Reed. Marsh Saint John’s-wort, an uncommon northern species, has also been found in the shrub swamp. While these species occur throughout Michigan, their distribution is generally concentrated north of Michigan’s Transition Zone, the broad division between northern and southern flora in Michigan running roughly from Muskegon east to the Saginaw Bay and across the Thumb. The northern plant community on the preserve is somewhat disjunct from its usual location north of the Transition Zone, but this is characteristic of the flora in the Port Huron area, influenced by the cooler growing season and extensive sand soils near Lake Huron. Historic fire disturbance may also have been another important factor in maintaining the northern flora.
A further unique aspect of the vegetation on the preserve is the occurrence of southern species, especially on the sand ridges, that enhance the vegetative diversity and create a blend of northern and southern flora unique to Saint Clair County. Distinctly southern species on the preserve include Black Oak and Pin Oak hybrids, Black Gum, Sassafras, Juneberry, and Smooth Highbush Blueberry. This north-south quality of the area’s vegetation was described about 100 years ago by noted Port Huron botanist Charles K. Dodge.