I don't know a lot about that species so hopefully someone here (or in whatever forum related to the species is) but if you can't you might try air layering a branch. That way you could have a plant establish faster than by using seeds or smaller cuttings.

That's a shame, Paul.
Berberis are some of the coolest little bonsai I've seen.
I was real tempted last year to purchase a plant to shape.

Why are they banned?

Josh

You (that's the collective 'you') can expect the best results for bonsai with B. thunbergii, unless there are other species in the genus I don't know about that are as predisposed to forming a trunk as thunbergii. Most, if not all, other species are more bramble-like, with a propensity to form innumerable canes instead of a trunk.

I do have a wonderful little slow growing dwarf I've been tending for several years that will one day make a very nice 'flame style' plant. I just wish it was green instead of purple.

Al

I had one with a 3/4" trunk and It died after 5 years. It was a nice little shohin and I tried to put it in a smaller shohin pot and it did not make it. I think it would still be alive if I had waited until the following spring. I do miss it.
Al
If you put it in the shade it may turn green like the one I want to split did.

I do appreciate the suggestion, Paul. Thank you, but the plant is B thunbergii atropurpurea 'Bagatelle' and the purple (burgundy, actually) foliage is dictated by the plant's genetic code.

Al

Al
The one that turned green in the shade is a red pygmy.
Paul