You'd have better luck planting them at the base of the hill .. plants grow toward the sun .. it's called Phototropism and is stimulated by chemicals in the plants called auxins and the roots grow down, that's called Geotropism or Gravitropism which is a response to gravity. Growth below ground is called positive geotropism and growth above the ground is negative geotropism. Photo/Geotropism is very interesting and worth looking into a bit more.
