Fall pruning: before or after leaves have fallen?

[Paradox]

@MACH5 had a conversation with Ryan, and Ryan brings this up on almost every stream that has a question about fall cutback. In the case of Sergio, in his location he experience negative reactions from the trees, dieback, etc... when pruning at leave fall. This is why he does it in spring. So I guess it is not "all inclusive" and dependent on the location that you are. Must be an NY/NJ wood nymph messing up with Sergio's trees.

This is good to know as I am not far from Sergio

 

[MichaelS]

The time to prune Japanese Maples where the roots are not being cut is at leaf fall when sap is being withdrawn or at the least sap pressure is reduced. When half or a little more than half of the leaves have gone is optimal. If you cut roots you have a much wider window. Here I mean substantial branches of course not summer trimming of extended shoots. This my experience based on Japanese advise where climate is rather mild in autumn.

 

[MACH5]

Just to explain again my approach since my strategy has changed in the past few years. I think it is better to cut back after leaf fall. The logic behind why this may be better than spring is that you allow the tree's weakest and/or adventitious buds to gain strength throughout the dormancy period and will be better able to open and develop when spring comes around. The secret in bonsai is energy balance!

 

[Shibui]

When trees are shown in full autumn colors, have they simply been pruned at the “wrong” time for the sake of a show? Dumb question but I’ve been trying to figure out an exact answer, as I have maples that have extended growth that I’d love to see in shape for the autumn explosion.

There is not really one 'right' time for pruning. Well developed bonsai are trimmed whenever the shoots grow out past the chosen silhouette. Developing trees are often allowed to grow long shoots to add some extra thickness to trunks or branches.
For a show, I would expect the tree to be in the well developed class so would normally be trimmed regularly right through the growing season.
If your tree has really long branches that have not been pruned all summer it is not really ready for a show. Even if you did prune it, the tree is likely to look a bit bald. Any pruning for a fall colour show would be done way back in summer to give the branches time to reshoot. No problem with pruning in summer.

For fall shows maples are often defoliated a month before which removes all damaged leaves and gives us a fresh crop of undamaged leaves that will colour much better than sun or wind damaged leaves.

 

[ajm55555]

Just to explain again my approach since my strategy has changed in the past few years. I think it is better to cut back after leaf fall. The logic behind why this may be better than spring is that you allow the tree's weakest and/or adventitious buds to gain strength throughout the dormancy period and will be better able to open and develop when spring comes around. The secret in bonsai is energy balance!

I reached the same conclusion Sergio. Thanks for confirming your current strategy

 

[Maiden69]

If I think about a SPRING hard chop.... the tree is still spreading resources out and may not react optimally to a local hard chop. But I have never done a spring hard chop...

From my understanding one of the benefits of doing the cut after post flush hardening is that the growth from this pruning will be "weaker" with shorter branches and internodes. Which is why it is recommended for secondary and tertiary development. I think it is some of the "science" behind Walter Pall's hedge pruning, where he chops all the strong spring growth to the silhouette of the tree, inducing copious back budding with tighter ramification that he can then refine to.

 

[badatusernames]

There is not really one 'right' time for pruning. Well developed bonsai are trimmed whenever the shoots grow out past the chosen silhouette. Developing trees are often allowed to grow long shoots to add some extra thickness to trunks or branches.
For a show, I would expect the tree to be in the well developed class so would normally be trimmed regularly right through the growing season.
If your tree has really long branches that have not been pruned all summer it is not really ready for a show. Even if you did prune it, the tree is likely to look a bit bald. Any pruning for a fall colour show would be done way back in summer to give the branches time to reshoot. No problem with pruning in summer.

For fall shows maples are often defoliated a month before which removes all damaged leaves and gives us a fresh crop of undamaged leaves that will colour much better than sun or wind damaged leaves.

Helpful, thank you! I have a trident that just keeps throwing growth and was getting curious what I may have been missing.