Our friend Doug Luchetti is a source of great stories and ideas. He reads and contemplates voraciously, and shares what he finds.
This piece on Fruit Walls, a forgotten piece of low tech agriculture, seems a timely reminder of how much worked perfectly well before we got smarter and messed most of it up. Before we all go out and start slinging bricks, look at this second pic of an old English version – one good wall might just be all ya need.
Our little 700 square foot home has one big west facing wall that gathers copious amounts of afternoon sun – seems a little vertical gardening there is in order this spring – Stay tuned!
UrbanMonique 
The only issue is that trellising espalier on wooden walls is not a good idea (mold, bugs, etc.). Brick or stone ok, but it’s important to leave some air space between the training wires and the wall (usually 12-18 inches). Espaliered fruit trees can be grown in large tree pots and moved (carefully) if need be (best done when dormant)