I did cut of the trunk down to the highest water sucker growing out of it. First did a scratch test and the trunk showed no green, but when I cut it off I could see the slightest bit of green beneath the bark. Maybe I should have waited until that part of the trunk turned brittle, but now at least the tree can at least put its effort toward making food and feeding its roots with those lower water sucker branches that are growing out of the trunk. Then maybe next year the roots will be established well enough to send up some shoots from the roots and I could then cut the old trunk down and allow the tree to focus its efforts on developing new multiple main leader trunks that should have better balance between them in trunk diameter.

There's no mistaking the leaves of river birch (Betula nigra) for paper birch (B. papyrifera). Bear in mind that paper bich bark is reddish in young trees, and then goes into white.

Yes, I have seen the three tree method that some growers use to produce multi trunk ornamental trees. I even planted a paperbark maple tree that had been handled like that. One of the paperbark trunks dominated and the other two died off each at different times. It did not seem to matter what I did to try and save those, they still died while the dominant one thrived as if no stressors of any kind existed for it. Also planting three young trees together is the technique I myself had tried to get a multi trunked River Birch tree. Five years later, one of those trunks thrived and now has a 3 inch wide trunk with beautifull pealing bark, and which has grown to about 10 feet tall. The other two trunks are currently about 4 feet shorter, also with some bark pealing and with only about 1 inch in trunk diameter. This drastic imbalanced look is why I dug the two shorter trunks, and now have them in bare root form. I have seen other reports of people having success at growing a new single main leader by the cutting back nearly to the ground of the damaged main leader. Of course those damaged trees are usually fairly well established. So I do not know why I could not do the same thing with my single trunked birch trees. That is, as long as I do it at the right re-established root development point. Is this truely a bad idea? I do think that my trees are nearly twice as mature than what past growers generally used for clumping out multi trunk birches, but if I do not begin the process to eventually prune out the current one inch wide trunks for these two trees; they too will likely dominate too much over any new sprouts which I might get to pop up out of each of their own root balls. I have also seen what you suggested concerning the trunks of clumps spreading to far; that is on a neighbor's birch that has only two leader trunks, and which is almost 30 years old. Is my only other option to keep them as single trunked trees. Is this delima, also why I have had such a difficult time finding young multi-trunked Heritage birch trees at my local nurseries. Also am I wrong in thinking a three trunked rootball would tend to grow more slowly and end up with less height potential if all three trunks emerging from one rootball grew at a relatively well balanced rate, and no trunk is allowed to remain, which seemes to so drastically dominate over the other two.

The purple spike flowers could be Bugleweed- a weed ajuga with green leaves. Arum italicum has leaves during the winter and goes dormant during the summer. It is an interesting companion to hostas. It puts up a bloom in the summer that matures into red berries. For the part sun, look into geraniums- Crane's bill. Some of them are evergreen- except the leaves turn red in autumn. Carex morrowii- Japanese sedge is an evergreen, grass-like plant for shade. There are other Carex as well, but not all are evergreen. I'm not very surprised by your purpleheart- mine has been around for 3 years. I am impressed by the z6!