Its seems you did well last winter, yet need to do more frequent copper sprays for your maples etc and switch to bark nuggets vs leaves.
To answer your question, It all depends on whats in your collection and your microclimate. For example @Osoyoug is near the water. We are further towards the mountains. Different microclimate.
One of the myths that seems to persist in bonsai in regard to overwintering is the observation “All the trees survived the winter” so they are healthy. Followed with the thought “thus the bonsai is robust and resilient enough to withstand the rigors of bonsai training this year this year.”
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Just because a bonsai “survives“ the winter doesn’t mean it hasn’t gotten its roots damaged. Bonsai Heresay has a good write up on this topic. Interesting how trees the roots of some trees one thinks as hardy are far from cold hardy.
A large pot may not freeze through, but the roots around the pot likely might… enough to cause damage, especially to the fine feeder roots. When this occurs there are dead roots mixed in an area where new roots are trying to grow. Experiments done here last year with probes and thermometers all through last winter demonstrated this situation. Also the root temperature differential on a bench at times was 7F less the in a pot on the ground. (
See resource)
While some species tolerate this situation (dead rotting roots) others are negatively effected. For example, Rick Garcia in Satsuki Azalea Bonsai, mentions that azalea roots will not grow where dead roots are.
cheers
DSD sends
