ABSTRACT This study evaluated the ability of bigtooth aspen (Populus grandidentata Michx.) patches to contribute to the understory diversity of southeastern Ohio’s mixed oak forests by providing unique microenvironments embedded within the larger mixed vegetation matrix. Twenty bigtooth aspen patches and adjacent mixed oak forest were selected for study. Microenvironmental parameters were assessed in both the patch and surrounding matrix and included light, relative humidity, soil and air temperature, soil moisture, nitrate, texture, pH, O and A horizon depth, organic matter content, and cation (Mg, Ca, P, K, Al) availability. Spring and summer vegetation surveys were conducted to investigate differences in floristic composition between aspen patches and surrounding forest. A MANOVA revealed significant (P , 0.001) differences in the microenvironment between aspen patches and the oak matrix resulting from differences in soil texture, organic matter content, soil and air temperature, soil pH, magnesium, calcium, and aluminum availability. Vegetation surveys demonstrated that aspen patches had greater vegetative cover (P , 0.05) and species richness (summer survey only; P , 0.05) than the surrounding mixed oak forest. However, ordinations did not reveal distinct compositional differences based upon the presence or absence of aspen, suggesting that although community structure and environment differs between aspen patches and control forest, bigtooth aspen does not support a distinct and consistent flora beneath their canopy.