Good post, Joe. I’m a bonsai enthusiast myself and I actually have one that’s very like this but not quite as big - maybe 12 trunks.
I have developed a method of doing bonsai that’s a little more in keeping with our western lifestyle - that is, while the Japanese method requires them to water their trees every day, because they are planted in shallow dishes exposed to the air, I plant my bonsai in our own normal standard reddish western-style terracotta flowerpots.
I then plant these pots in the ground.
To a certain extent the pot confines the roots. Burying the pot allows the plant to be watered by the rain and also protects the roots from drying out or being burnt by the sun. Furthermore natural rainwater does not include the mineral content of tapwater so whitish mineral deposits do not form or build up on the soil surface as they do over time when watered with tapwater.
I call this western style bonsai, because our busy lives often don’t leave us much time to do things at the slower pace of the traditiona oriental way.
Using my method, I can have the look of bonsai in the ground without having to water my trees every day.
I can lift the pots right out of the soil for occasional pruning of the branches, perhaps once a year. Twice if I’m going to show them.
As for the roots, they do have more room to grow in a western pot than a traditional Japanese bonsai dish. Moreover, the roots are inclined to find the drainage hole and escape through it. So I keep a close eye on the root development.
The plant can usually be popped out of these pots quite easily for root inspection. Any thick root that has escaped, and that might even be locking the pot into the ground, will get lopped off. I generally try to limit root surgery to once every couple of years, and also try not to do too much at a time as I believe this is quite traumatic to the plants. This is not always possible, especially with plants that have an aggressive root habit. In time, however, plants seem to ‘learn’ to slow down their growth, both abobe and below the surface.
As for ground covers for my bonsai, for reasons unknown I have not had good luck with any of the true mosses at all. I have had to depend on Irish or Scotch moss, or other miniature ground cover material.
You mention dwarf plants and how they can take off and become oversize for our railroads.
This is very true. I have seen dwarf Alberta spruce as high as eighteen feet tall.
When I was a kid my Dad planted what were then called dwarf fruit trees. At maturity these trees were considerably smaller than standard trees, but they were easily twelve feet high.
This was over half a century ago, and I’m certain that things have changed since then.
All the same, in the horticultural world, as you, Joe, are probably aware, a distinction is made between the terms “dwarf” and “miniature”. What we really want is “miniature”.
When we go shopping for plants for our backyard railroads it would be wise for us to bear this distinction clearly in mind.