My place has a collection of walnut
trees, a couple that are upslope, then a bunch of younger ones that fan out below them. I'm going for the "try it" technique. Because if nothing else, who knows how the people who made up the lists were growing their stuff? If they fertilize, sprinkler it, etc, is that the same results as deep mulch and soil held moisture? Was the shade from the tree affecting the growth, depending on the light levels under it? Were there other plants that were helping or hindering?
In the end, there are SO many factors that can affect growth or non-growth, that experimenting with your own parameters is really most effective.
If your plants in pots are heat stressing, have you tried burying the pots? That helps a bit (not 100%, but a bit. They still want more root/water room.) Maybe bury half the pots, and plant out the other half, so if your planted ones die off, you still have stock. If they do well, pull the pots out of the others.
I know a song, (that no one else seems to) that the tag line is "why don't we try... EXPERIMENTS!!" that I often sing when I'm doing weird things to plants. I moved from the desert, where I had a lot of stuff growing that I was told "you can't grow that here!" Oh, I didn't know, so I didn't tell the plants, so they didn't know either! Microclimates are your friend....