I looking for a small tree, 12ft max., to put in a tricky spot on a south-facing wall. The site is about 5ft x 5ft. on top of a retaining wall and it's tough to get to to maintain. It's along the neighbor's fence--they have concreted their backyard so I don't want any mess to spill over the fence. Lastly, it's above a patio where I keep container plants, some are roses, so the tree needs to be airy to let the sun through. The reason for a tree is part screen from the neighbors yard and part beauty when looking out a bedroom window. Thanks for any suggestions.