I have a wall running up the middle of my garden. About 1-1.5m/3-5ft tall, it forms part of a flood defence to the river that is south of us. On the south side, it's great, which means I have an essentially south-facing growing space. However, on the other side - which is where most of the garden is, I have a north-facing wall. However, its not that high. I had intended to plant mainly shade bushes along it on this side, but I've also wondered about dwarf rootstock fruittrees and small trees. I might be able to create some sort of miniature food forest.
My question relates to the establishment - if I tried to do this, could I establish trees? Bare root would be my preferred planting, but then for the first year or so, they would be in deep shade; would that be OK? How will trees perform if their canopy gets light, but much of the rest of the tree does not?
The following may not apply near you, but would around me. Do you own this wall, or is it owned/maintained by others? I would be concerned about making a long term investment of planting near something like you described, as it could need removed as a threat to the wall or for maintenance. Also you may face challenges later if you wanted to remove the trees near the river (fines).
From a growing perspective I think a tree could coexist with the wall just fine. Many trees are used to less light early as they would be understory in the forest. If it worried you, you could put a reflector on a couple posts further to the south to give the plant some light until it peeked over the wall. Low down in the south side of the wall would be good for "zone pushing", but trees would outgrow that unless espaliered.
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