AusBonsai

I have this Larch that's I've pruned and wired. I took it out of the pot and found that it's quite root bound. Should I prune the roots back or leave it until next spring?

It’s not that root bound, there’s still dirt in the pot. Any plant in a round pot will circle like that in one year. Looks pretty tame to me. I cannot answer your question re: timing though.

Leave it until winter


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I do not know how larch respond to growing season root pruning. They are quite sensitive to many other environemntal factors so I would not expect larch to like summer repotting. Beano is on the right track. Often the outside of a root ball looks really bad because that's where most roots circle but inside is still fine. The real issue with root bound is ability to take water. A severely root bound tree has no spaces left in the pot for water and trees do suffer.
If you can still get water to penetrate then leave it for now. If it is just a bit iffy leave it but make an effort to soak the pot each week. If it is really so root bound that water just will not penetrate and the tree is at risk then you can't lose by repotting now.

I would also consider a deeper/wider pot if you can't ground grow. There is mention of optimal root growth depth