MrWunderful
Omono
Perhaps, but given that this place is a bonsai nursery and doesn't do anything else ( except succulents), I have to assume they are properly potted. I can call and find out to be sure.
I understand where you are going.
They have a minimal amount of what most enthusiasts would call actual bonsai, as they sell mostly field grown and pre-bonsai stock (still some of the best material in bay area)
If you look at the more finished trees in nice pots next time you are there, you will notice the soil medium is different with those trees.
Using soil specific to bonsai is not required; but if you are looking to have the tree be the best it can, I suggest doing a minor amount of research online or on this site about “bonsai soil” to see a million different opinions. It will get you started on the reason why its such a controversial topic.