Exposing the fine root-hairs a little at a time will naturally air-prune them.
For the most dramatic results, clean the roots when you formally root-prune and re-pot.
The key is going to be working gradually.

Josh

Thank you Josh. I realy didn't think of nebari also being gradual. That's true, the air will naturally prune the root-hairs. OK, so if I can't see the good nebari yet I will see it soon I hope.

Thanks again,

Gardener Guy

No problem!
What kind of trees are you using?

Josh

The trees with the tangled roots are norway spruce and a maple. But my bonsai collection includes Red maples, sugar maple, one silver maple, apple tree, Norway spruce, Alberta spruce, Scots pine, Azalea (pink), Virginia creeper, river birch and some others, just to name a few. Most of them are in training as of now.

Gardener Guy

Some tips on how I create surface roots:

If the trunk calipers are small (under 1") you can look at the best roots and determine where you want the buttressing roots to occur with the idea that everything below that point will be removed in time. I often take a couple of heavy zip ties and secure them tightly around the trunk just below this point. I then put the plants in the ground and wait. You can do it in a deep container by planting so the ties are a couple of inches below the soil line.

As the cambium swells, water movement upward through xylem tissues remain largely uninhibited, so the canopy still gets water, but photosynthate transport downward through phloem tissues becomes restricted, so photosynthate builds up immediately above the restrictive ties. This gives rise to roots and a swelling or the beginning of a root flare immediately above the restriction. As new roots emerge, the old roots are starved of photosynthate and die.

I do a lot of cuttings, and all m y cuttings are treated this way. Sometimes, if the cutting lends itself to this procedure: I slide a 1/4" Lexan disc (3-4" diam) over the cutting and secure a zip tie below it to keep it from slipping downward. I stick the cutting with the disc 2" below the soil line. As the disc restricts root growth, roots emerge above the disc and are forced to grow horizontally for at least the diam of the disc.

For older trees While repotting, I look at where I want roots to emerge. I'll use a brad-point drill bit (1/8 or 3/16 depending on the size of the trunk) to drill only through the cambium. I spin the drill between my fingers - I don't use a drill motor. This makes a very clean hole, which I then fill with rooting gel, using a piece of wire dipped in the rooting gel. I then finish the repot and pack sphagnum moss (not peat) around the wounds. Roots will have appeared at wound sites by next repot.

Alternately - start cuttings & thread or approach graft the cutting to the bonsai material. Once the cutting has completely fused at the graft site remove the top part by cutting flush to the graft site so only roots remain.

Al

Thank you for that Al. That was very informative.

Gardener Guy