Heavy pruning in spring for Thuja...

[Cadillactaste]

So the Canadian bonsai group state spring for heavy pruning of thuja. I have decided to wait on roots one more season and really thin the top. Will just add some substrate to the rock from some washing away. IF ... I can safely do it now. I have never really done more than offer horticutural needs.

Anyone wish to offer direction? Spring...do they mean now, or was it really spring when still dormant?

 

[RKatzin]

I just gave my Rheingold a good trimming. This gets a real burnished look to the foliage during winter. When it turns back to golden is when I give it the first trim. To keep it looking like this I'll have to trim it at least twice during growing. I don't usually get to it but every couple of years when it's become a big golden mound. I need to get it out of the grow box and reduce the roots significantly to curb it's exuberant growth.

 

[Tieball]

I always believe it is Spring when I see buds swelling. The timing....it’s different on my different trees. But generally....right about now for most of my trees.

 

[Cosmos]

David Easterbrook of the Montreal Bonsai Society says that heavy structural pruning should be done in the Fall, along with creation of jin/shari, starting in late September:

"La taille de formation (branches et structure), ainsi que l’ajout de jins et de sharis, s’effectuent à l’automne, à partir de la fin du mois de septembre."

https://bonsaimontreal.com/nouvelles/fiche-technique-thuya-occidental/

For you guys further south, that would mean well into October, possibly.

 

[RKatzin]

I am not doing any structural pruning at this time. I am only trimming back the foliage to my structure. It will need another trim midseason to keep the foliage in check. I have tried letting it grow into a weeping form, which it does without much assistance, but I like it better trimmed back with the branches exposed.