In order to have foliage follow the normals of the geometry it is being placed on, first check "Align to Normal." This will align the foliage to whatever normal there is of the geometry it is placed on.

If you want the foliage to appear upside down, you will want to change the "Align Max Angle" to 180 (the opposite of Z-up; 0) and increase the Ground Slope Angle to 180 as well. You may increase variance by adding a Random Yaw and changing the Random Pitch Angle as well.