Factors important to tree growth in the Midwest are generally related to moisture availability. By relating site quality to site and soil characteristics of forests, potential productivity can be estimated for non-forested areas. Our study measured the growth potential of black walnut in natural stands. We looked at 28 stands on unglaciated soils in the Flint Hills of east central Kansas and evaluated numerous environmental factors including site and chemical and physical soil properties. These factors were related to tree height at the standard age of 50 years. Simple correlation and multiple regression analyses were run with site index using 31 variables of soil and topographic characteristics. These analyses explained 80% of the variation in height with chemical and physical variables. Soil type and depth to a restrictive layer (DRL) accounted for 55% of the variation in height.