Gardening and Horticulture - Eucalyptus Tree Roots

I'm planning on planting a eucalyptus tree in my backyard in a corner next to an eight foot high block retaining wall. My backyard is the high side of the wall. Do I need to worry about the eucalyptus tree roots underminding my retaining wall? Do eucalyptus tree roots grow down or spread?

Some trees put down a substantial tap root, but all of them grow roots out in all directions in to top foot or so of the soil, with fewer as you go deeper. Depending upon how close this tree is to the wall, it may well send roots throught the wall in places through natural growth patterns. These roots will stop once they reach the surface. I don't think it will undermine the wall to a depth of 8 feet. The tree will ordinarily develop to accommodate its surroundings. I think it would be wise to place the tree back from the wall about 10 feet. Eucalyptus trees grow to a fair height.

Hope this helps.