Question
We had two honey locust trees in our backyard, but they were beginning to compromise the 4' retaning wall with our neighbor so we had them cut down in February 2012. Our yard faces South and West. I thought a River Birch would be nice there, but now I'm not sure what would be best. We miss the shade, but don't want a large shade tree for future owners to worry about the wall in the back. The space is about 35 feet, between house and wall. We'd like a tree with deep roots. What would you suggest. We live in New England about 10 miles West of Bosotn, MA.

Answer
Here is a list of trees that the Boston Urban Forester recommends for that area. I would go with one of the "shorter trees" It will depend on what you want--flowers fall color etc..  I would look at Goldenraintree, Japanese Tree Lilac for flowers and Persian Parrotia, Persian Ironwood or Hedge Maple or Amur Maple (Single-stem) for Fall color. The root systems of these should be fine.

You also might try calling the Forester and ask him which he would plant. He would know local conditions and tree that do well in your area. This number should get you the information 617 635-PARK (7275).

http://www.cityofboston.gov/parks/streettrees/Tree_species.asp