I am planning on using Eastern Red Cedars as a screening plant on top of a retaining wall. The only problem is the wall, which was just build, is ten feet from a rod iron fence. The roots have plenty of room to grow away from the wall, but because of the fence I will have to plant the trees about five feet off the wall. What is the likelihood of the roots damaging the wall?

Slim to none if the wall is built soundly.