Pinus densiflora (Japanese Red Pine) from Telperion Farms - progression

[River's Edge]

In his experience, cutting a coarse root will result in new roots only at the callus and having to cut it back later would set the tree back.

This is only true if there are no feeder roots off the coarse root between the base and portion cut. Boon always instructs one to reduce roots being sure to leave portions with feeder roots attached for that reason. If you are reducing a thick root without feeder side roots then you might as well reduce it as far back as you need to the first time.

So he feels that the greatest reduction needs to be at the first repot.

Interesting statement! Cannot see how that fits in many circumstances of collected trees, or even in nursery raised trees that require staged reduction in order for the tree to survive.
Certainly makes sense in that it is the best opportunity to assess and make major changes to the root structure if the tree's condition will allow that to be done. Given that conifers typically are approached with 1/2 HBR the statement seems a bit ridiculous in that half of the root ball would be original size and thus not reduced to fit a bonsai pot.

Not questioning Ryans comment, simply the interpretation of that comment to many situations that one finds in Bonsai practice.
Perhaps like many generalizations their is a certain amount of truth in the comment.
And a lot of misunderstanding of when it can or should be applied.

 

[PiñonJ]

If you are reducing a thick root without feeder side roots then you might as well reduce it as far back as you need to the first time.

That’s the whole point, but he’s not just referring to thick structural roots. He means any coarse root, which in pines is most roots.

Given that conifers typically are approached with 1/2 HBR the statement seems a bit ridiculous in that half of the root ball would be original size and thus not reduced to fit a bonsai pot.

Ryan doesn’t half bare root, that’s a Boon technique. We tend to do large initial reductions at Mirai, once a tree has established a strong root system in its grow box. Conifers, however, are never bare rooted and some portion of the root mass is always left untouched. Nursery stock already have a lot of roots, so the first action with them is to get them into a bonsai container with free-draining substrate. The comments above, about the greatest reduction needing to be done at the first repotting is specific to pines. I don’t have sufficient experience to give first-hand accounts of all of Ryan’s observations, except to say that the repotting techniques that I’ve learned from him work really well for me. And the trees at Mirai speak for themselves. Just thought you might be interested to hear about the rationale for the technique.

 

[River's Edge]

once a tree has established a strong root system in its grow box.

Now that you mention the circumstances under which you take this approach it makes more sense and is not that different from other professionals. It helps if you provide context for your comment.

 

[PiñonJ]

Yesterday, I did shoot selection and needle plucking, and I removed a couple of branches which would lead to structural flaws. I also re-positioned some branches, as well as the apex.