Due to different amounts of solar exposure, opposing sides of a hill have different levels of irradiance, temperature, soil water, and nutrients: west- or south-facing slopes are brighter, warmer, drier, and less fertile than east or north facing slopes (in the northern hemisphere). We test if these differences are substntial enough to cause changes in flora distribution of the foothills in northern California. Our results indicated that indeed, flora distributions are consistently different on opposite slopes. In particular, a potentially drier, less nutrient rich grass is more abundant on west-facing slopes while east facing slopes favor a possible more moist and nutrient rich grass. A variety of improtant extensions to this survey are suggested.