Problems with nebari of Elm. What correction technique is better?

[proninyaroslav]

Hi. I have two elms, their age is about 10 years, and both have a similar problem: the central root isn't in the center, but on the side. These elms grew between the stones. I made a sketch of how this root looks out.

Spoiler: Nebari sketch

It will not be possible to completely remove it, because it's located on the side and there are no other roots in this place closer to the trunk. Therefore, I see two options for correcting this: the first is to split the thick root into two thinner parts and grafting roots closer to the trunk to them. This is a rather complicated procedure, besides, the result will still not be perfect, but there is a second option that makes me doubt: to make a ground layering above this root. It's a bit scary to remove a strip of bark around the trunk, because if ground layering isn't successful, the tree will die. I decided that it was possible to go a safer way (tourniquet method): pull the wire at the base as a tourniquet, so that it crashed into the bark, and cover this place with soil and sphagnum moss.
Which of the above methods is safer and more effective in this situation?

 

[BrianBay9]

Ground layering with elms should be a very reliable proposition. That's the approach I would take.

What kind of elm? Generally where are you located?

 

[WNC Bonsai]

A picture is worth 1000 words!

 

[proninyaroslav]

This is a local elm species, I think European elm. I'm in Russia, USDA 4~5.
P.S: If you choose ground layering, which way would you choose: a tourniquet method or a classic method with bark removal? Speed isn't important to me, reliability is more important.

 

[BrianBay9]

I have only done the more typical method of removing bark around the trunk.

 

[Adair M]

Cut the ring.

The tourniquet method has a high failure rate.

 

[Shibui]

There is also the combination of cut and wire. Make a narrow cut, just wide enough to fit a thick wire, all round where you want the roots. Then place a piece of wire into the groove, tie the ends and twitch it so it is tight in the groove. Hammer it in if there are places it is not sitting against the wood. Then cover as normal for a layer.
Wire prevents the cut from closing and roots seem to grow well this way.

If you are worried about failure causing the tree to die then layer in spots. 2 methods I know of:

1: 'tooth pick' method. Drill holes through the bark and into the wood below. Dip a matchstick (not the red end), toothpick, piece of skewer or similar into rooting compound and insert it into the hole. Drill as many holes (and plug with sticks) as you want, in places where you want roots. Sticks prevent the holes from closing so roots are more likely to form at those spots.

2: 'wedge' method. Use a small chisel to lift flaps of bark in places you want roots. Hold the flaps open with whatever you have handy. I have seen small plastic tiling wedges used for this. Treat the cut areas with rooting compound and cover as normal. Results are similar to other layer methods but you have more control over where the roots form. Some roots will form at the end of the flap which is already wider than the existing trunk = wider spread nebari straight away.

As neither of these totally ringbarks the tree it will continue to grow even if no roots form and eventually the cuts/ holes will heal over of you allow it.