Question
Hello Sean and thanks for taking my question.  I live in a two-story colonial-style home with wrap around porch on 3 acres.  I have 6 established pin oaks (age: 17 years each, about 40 ft in height) that are located about 30 ft from my front porch and follow the semi-circle route of the porch around the side of the house.  There is a very slight grade in the ground running between the porch and just past the base of the tree path.  

Currently I have only some single layer 4x4 ground level landscape edging timbers encircling each tree.  I have been giving some thought to removing these old edging timbers and replacing them with possibly some low-height landscape blocking for a more finished look and also adding accent lighting under the trees.  However, I'm questioning whether this is even feasible given the root system of these trees.  If I  trench around the trees to provide for a base prior to installing the blocking system, I think I will encounter the root system immediately.  Is there some alternative ring approach I can use?  

In my minds eye, having weathered stone rings around each tree makes for good aesthetics but I don't want to damage the tree systems themselves. I merely want a classy landscape look to enhance this new porch I just finished building.

Many thanks for your consult!

Kevin McGrath

Answer
You can not do this if it involves trenching within 20 feet of the tree. If you must have something as a wall, then use larger flat stones and stack them up using gravity only to hold them together. This way they can move when the roots grow. You may have to re-stack them occasionally but your tree will be healthier for it.
Best of luck.  PS also see my answer to nearly the same question a few months ago (Hardscape Tree Ring)

Sean J Murphy, LA,ISA, LEED AP
Please check out my blogs and articles on landscape topics like this on my websites.
http://www.seanjmurphy.com
http://amenityarchitects.com