As per request of @GigiPlumeria, this is a step by step on how I do an adenium root training, I believe there are a lot of other method to do it, and this is just 1 example of how I did it. Hope you find this useful , and feel free to comment, ask , or add any other missing information.
I have performed this for more than 10 adeniums, only 1 failed.
As the purpose is to show step by step with picture until we have the roots that we want, this will take around 1 year until we can see the result, to cut the process of waiting for 12 months, I will use different adeniums at different stages.

Special note:
1. As I live in Indonesia with tropical climate, no winter, I have no idea how other climate, especially winter will affect the growing process of the adeniums, and no idea whether adeniums will go to a dormancy stage in winter.
2. This process is just base on experience or what is available, it is not necessary is the right approach, please feel free to improvise and explore new ways.
3. Please do not do this with your expensive Adeniums, just try it with some seedlings that you can afford to lose.
4. On top of the standard root training process, I also make other experiment for my own interest, just consider those as a 'by product', not part of the root training

I recommend to do this with 2 to 4 adeniums at once, incase 1 or 2 die, we still can continue the process, not to waste 1 year.


Stage 1. Seedling selection criteria
- diameter or the caudex ( 2 - 4 cm)
- the height of the plant 12 - 20 cm , if the plant is too tall, it can not stand without any roots
- select the plant that is straight, not bending to 1 side, for the same reason as above

Tools required:
- a sharp knife
- fungicide , or shallots (thanks @Wildbloomers), ( I never use shallots btw)
- small pieces of styrofoam or plastic bottle cap, or small piece of tile, anything that is hard and can be used to support the plant, the size is slightly bigger than the diameter of the caudex

Below are the step by step with pictures:
1.A. seedling selection, you may see that the one in the middle did not meet our criteria, it was too long and bending ( just ignore it for the time being, that is my sub-project), I also have a feeling that the one at the right looks like too old, lets see how it goes


1.B. Cut them at the widest part of the caudex (please make sure the knife is sharp and clean) , for the one on the right, trim all the small roots that's still available at the trunk


1.C. Trim the edge of the caudex by around 1.5 mm, when we air dry them in the next view days, we will like the skin of the caudex to shrink upward, not downward, as there is where the new roots will grow, we want the roots to grow outward


1.D Apply fungicide to all the wounds, then let them air dry for a couple of days, maybe 3 to 4 days, my criteria is to touch and feel the wound at the bottom, until I feel that it is hard, not soft. Please do not expose them to sunlight for now, just keep them in a place that is bright, good ventilation, and no direct sunlight.


1E. Cut some of the leaves to reduce evaporation, usually I like to keep around 4 - 5 leaves per branch


Now relax and don't worry too much, I was very worried when I did this for the first time

Additional information on step 1D, there are a lot of people who does not have fungicide, they will use shallots ( red and small Asian onions, not the sweet onions) , they cut the shallots by half squeeze it a bit to get the juice, then rub the shallots around the edge of the caudex, not the bottom, they said shallots can act as both fungicide and root hormone.

Also you may see that I have cut the adenium that is long and bending, please ignore that one, it is my by-project, usually we do root training, then later we will cut the adenium to have multiple branch, I just want to see if I do both at the same time, will the plant survive. By doing this we understand that the chance of it to live is smaller than the chance of it to die. I do not recommend anyone to try this.

And this is my sub-project, I try to grow the root, since there will be no node for them to grow leaves, if they can survive, then we will have an interesting plant, last time I used 1 for grafting, the grafting failed but the root survive, the tip of the skin turning green a bit, no rot and not fungi at all for at least 6 months, then I decided to make another grafting on it, and this time it die. I wish that I did not do the grafting, then I may have a big weird succulents, I assume that by turning green, it will have the capability to photosynthesis, and can get nutrients from the soil, they will leave and grow big, at the end of the day we may have something like giant lithops.
I keep 2 today, apply fungicide to one, and the other one just apply a grafting tape to reduce the evaporation, lets see how they perform

@Kaktus, thank you for this step by step process. I wish I have a seedling that size right now, I would have followed along. Others use "aloe vera" as a fungicide. I have not tried it but I bought an aloe vera for next time I need it.

On your last experiments, I have a few right now from when I chopped the roots of my adeniums from root rot. (Great minds think alike ). It's been a couple months, not a single sign of leaf but some roots are turning green. It is understandable that leaf
will not grow from the stump right away because there are no leaf nodes but I think they eventually will. Others shriveled away because I let them air dry instead of planting them right away when the roots were strong and healthy. So I might have a headstart on this last experiment if mine will not die. (I applied cinnamon, then I applied waterproof wood glue on the stump when they dried.)

Hah.. good to know that someone else is making the same experiments, i really hope that there will be no leaves..
I also heard about aloe vera and cinnamon, but people here prefer shallots as every house will have them in their kitchen.
Btw, what do you mean by bought aloe for next time usage? You bought a bottled aloe? I think what they meant is the sap of fresh aloe.

Very nice, Kaktus. Love the step by step.

Kaktus said:Hah.. good to know that someone else is making the same experiments, i really hope that there will be no leaves..
I also heard about aloe vera and cinnamon, but people here prefer onion as every house will have them in their kitchen.
Btw, what do you mean by bought aloe for next time usage? You bought a bottled aloe? I think what they meant is the sap of fresh aloe.

Aloe Vera plant, I never owned one. So I bought a small aloe Vera plant. I will try the onions too.

I have seen a number of videos that advocate using shallots as a fungicide. I've tried this with poor results. I'll stick with fungicide, it works for me.

Good to know. As for the stump, I want leaves. This stump has been like this since June and I don't think I want this to remain like a lithop with no face.



I'm guessing the branches will grow on the sides? I saved the other roots too and they are not dying but they are not growing.

After the cut has healed, I'm wondering if it would protect the bottom part if a waterproof wood glue is applied to the bottom before repotting? The reason I ask is that it probably will help later to make sure that it is sealed and will not be the starting entry of a root rot. My "stump" is shiny because I applied a wood glue so it will protect the top.

I had a plant just like yours. Kept it for four years. Gave it fertilizer, changed light intensity, repotted, even withheld water at one point (it just got soft). Anyway one day it just up and died. I wish I had grafted something onto it. I suspect that without a a growing point it just acted like a root with the top part making just enough chlorophyll to keep it alive. Kind of like rooted Hoya kerrii leaves that they sell on Valentine's Day. No chance of putting out new growth.

GigiPlumeria said:Good to know. As for the stump, I want leaves. This stump has been like this since June and I uli don't think I want this to remain like a lithop with no face.



I'm guessing the branches will grow on the sides? I saved the other roots too and they are not dying but they are not growing.

oh,
Last time mine still kept its white color and smooth for 6 months before it dies. If it change to brown like this, maybe I'll slowly create some cracks to make it looks like dioscorea elephantipes

GigiPlumeria said:After the cut has healed, I'm wondering if it would protect the bottom part if a waterproof wood glue is applied to the bottom before repotting? The reason I ask is that it probably will help later to make sure that it is sealed and will not be the starting entry of a root rot. My "stump" is shiny because I applied a wood glue so it will protect the top.

So far we never apply any glue, usually if it dries then should be alright, and I am worried the glue will introduce some fungi to grow.

When I cut the branches, sometimes to reduce the evaporation, I apply nail coloring on the top

Wildbloomers said:I have seen a number of videos that advocate using shallots as a fungicide. I've tried this with poor results. I'll stick with fungicide, it works for me.

Ahhh , After googling for shallots, it is what I meant by onions , in Indonesia we call this red onions and white onions for garlics , will see whether I can edit the word, thanks a lot...

I will also stick with fungicide...

And good to know that the stump can last for a couple of years, during that period, is it grow bigger in size ?

@Wildbloomers, that is very interesting to me too.I don't expect this to survive this long so just curious what it would do. I'm thinking maybe I need to cover it to keep the humidity because I haven't really been watering it.

@Kaktus The brown color is the cinnamon that I applied. Then when the top was hard and dry, I applied the waterproof wood glue.

I'm curious since some plants can be grown from root cuttings.

Unfortunately the root did not increase in size which is probably because the chlorophyll made by the green bark wasn't enough. And just as unfortunate, Adenium do not grow from root cuttings like some other plants. Of course I was hoping that it was high enough up the plant to act like a stem not a root. I wasn't so lucky, maybe you will be more fortunate. Good luck!

quick update on the project..
Because of the hot weather, the adeniums dries out quick, applied nail polish on the one that we cut the branch, and cover the root to reduce evaporation

Instead of nail polish, I use the recommended waterproof wood glue here. My experience, it helps reduce and sometimes prevent the shriveling of the end cut, if applied as soon as the end cut dries.

should be alright, as long as something that can be used to seal it. I have read also some people use super glue, for me is everything handy or free available at home.

Do a quick check on the adeniums, realized that we forgot to trim some of the leaves, has added the step in the initial posting