Would love to hear if there’s a good resource for this. In lieu of one, a great time to repot almost everything is right before the trees start growing in late winter/early spring. For the CA central valley, that’s early February.
- tropicals are better repotted when they are actively growing, typically during summer
- Japanese flowering quince ‘chojubai’ are better repotted in fall
There are plenty of other times to repot most bonsai, but those specifics depend on the variety and sometimes on the health of the tree. I’m already starting to repot my trees and will continue doing so into February and possibly into March for some varieties.