http://www.oregonlive.com/environment/index.ssf/2010/02/street_trees_increase_home_val.html
A lot of cities don’t even plant street trees, but this would seem to suggest (like we don’t know) that lawn trees also would enhance values, and that awful situations needing attention (hard to mow slopes etc.) that would cost money to solve will be turn-offs. But it’s amazing how many people don’t look at this consciously.