How do maple roots respond to root pruning?

[Shibui]

I sometimes see advice to leave roots long and that new roots will grow along the length of the pruned root.
This is NOT what I have seen. I always prune roots as short as possible because I noticed that the vast majority of new roots grow from the exposed end of cut roots.
Here are some photos of Japanese maples I dug out of the grow beds.


I think you should be able to clearly see how lots of new, smaller roots have grown from where the ends where roots were cut last year.

Just in case - the blue lines on this one show approx location of the cuts made last winter.


I have now cut all the roots on these back as shown in the final picture, first row before they go back in the grow beds or into pots for sale.

 

[QuantumSparky]

The advice that I'd gotten from forums/videos is to cut back all the large roots so they will do exactly what you've shown in the photos. I've also heard that maples are not one of the fussy species when it comes to root pruning so long as you do it correctly. I'd imagine that the masses of small feeder roots contribute more to the tree than the thick roots when it comes to bonsai so losing length on the big roots doesn't matter much if the feeders are good enough to sustain the tree.

This is all just knowledge and advice I've collected over the last few months though, as I don't have firsthand experience of root pruning a maple (not until next spring when I do mine!)

 

[Bonsai Nut]

Just to emphasize... @Shibui is south of the equator. This is not work you would want to do right now north of the equator.

 

[Shibui]

Interesting how we make assumptions that others will understand the concepts but that's obviously not always the case so thanks for qualifying @Bonsai Nut
The photos do not show bare trees but I do this sort of root pruning in winter and it is currently cold (for here) and rainy in my part of the world.

 

[HorseloverFat]

I assault Acer roots....

They(and Ulmus) respond SUPER well to drastic root action, in my experience. (WHEN it’s the appropriate time for such work)