There are many species of willow that weep. Many grow less than 20 ft tall. One of the tallest weeping willows is Salix alba 'Niobe', which can reach 60+ ft tall. European Weeping Beech (Fagus sylvatica 'Pendula') is a nice weeper that can grow quite tall. 2 pics below http://inlinethumb11.webshots.com/906/1381533667060568696S425x425Q85.jpg http://inlinethumb55.webshots.com/35190/1072897000038723424S425x425Q85.jpg

Dave, Ken, thanks for the links. When I'm down at the Missouri Botanical Garden next I'll check on their purple beech see how its holding up to the sun. That Crimson Spire Oak page has links to some more nurseries there. Thanks. I could even live with a few more feet of spread. That would definitely fit I love them Tulip trees big and open grown also. A narrow one would take some getting used to, but would fit in more suburban spaces. My neighbor has one he transplanted where I can see it all the time, only reason I'm not itching to get one myself. Again, thanks for the links. There are just SOOO many cultivars available its difficult to keep track even though I keep my Forest Farm catalog handy for reading in the bathroom lol.

Schefflera pueckleri does develop some rather aggressive surface roots with age, and may be perfectly safe it your wall has a properly reinforced foundation of concrete with rebar, but not enough info here to advise you in your circumstances. In general Podocarpus latifolius or another species is probably a safer choice if your retaining walls are of questionable construction.I've also seen Magnolia grandiflora dwarfer cultivars used as trained espaliers in narrow planters without foundation problems. As to just one 2 month drop of flowers for Bougainvillea, not how I see them work here in northern California where most cultivars have two to three waves of bloom throughout the year, and drop massive amounts of flowers. Not a vine I'd use by a pool without a pool cover.

Is house single story or taller in that spot? If single story, one of the cold hardy crape myrtle hybrids could work nicely with that spacing. Their long blooming season, fall color, and peeling bark could give the four seasons of interest you're after. We have ~20ft tall CMs dong well as close as 6ft from slab on clay. Integrity of plumbing and foundation are fine, so main engineering concern in our soil/climate combo is their effect on the moisture stability under the slab. We compensate with drip and sprinkler irrigation. There's almost no way to consistently prevent trees this close to a house from giving squirrels and other critters access to the roof. But figure you've already had to face this with the original tree. If the house is more than one story in that area, something with a vertical/fastigiate shape would probably fit better.