Hi Gerry, could you please advise on the best windbreak shrub for a site on the side of a mountain. North winds enter on the same level as the house. NW winds enter from above a rock face approx. 6 meters above sitel level. Windbreak needed on top of rock face. No space on ground level. Very little soil on NW side but lots of rocks so shallow roots shrub would be ideal. Trees would block the afternoon sun. Also any plants cannot be poisenous to animals. Thank you