@Bonsai Nut , I'm finally getting into the thick bark elm game. Seems reverse taper happens easily. Is that right? I found winged bark elm, and I plan to collect some. The trunk may be 1.5 inches, but the bark could be 1/4 to 1/2 inch thick. I think because the bark is so corky that it makes the base look puny. It's like I have to make the elm compensate by growing a fatter base. What I've observed so far is that they only have bark on the trunk, but will the surface roots bark up? Can they catch up if they do grow bark from exposure above ground?
The key to avoiding reverse taper is to not let the branches get too big, and to not let too many branches emerge from a single spot on the trunk (which is good design advice, regardless). You can also judiciously remove upper sections of corking bark, and reduce the trunk diameter by 1/2 inch or more without doing any cutting whatsoever. In the case of this stump, I am fortunate because no one trimmed at, so there is a lot of low growth and quite substantial flare at the soil line. However there are a few sections where multiple branches emerged from a single point (probably due to an old severe pruning) and no one reduced the branch number, so you get a "knob" of swelling growth. That will have to be removed, or designed around. It is very difficult to completely remove old knobs.
The other technique to use is a low ground layer - as low as you can get on the trunk. Not only will the trunk swell, but there is a chance you can get new growth low on the trunk which can help assist you in developing taper. But the truth is - no matter what you do - these trunks will always be "chunky" which is part of their charm. Embrace the chunk! LOL! Design for it
As far as the surface roots go, they will scale up, but I haven't seen any "cork" the way the trunks do.
