I don’t have any pumice, closest thing is perlite but that’s possibly too water retentive. I think the issue was long-standing, there was japanese (landscape?) cloth embedded in the inner root ball!
At least it’s rootball now “fits this pot”….gahhh.
I saved this JWP using the gravel method, also had “no roots”, but it was a close thing and took three years, and it lost most branches. The issue with this WAS compost/weevils:
Not 100% sure why but my Senjumaru (sport of Kotobuki) JBP has suffered total root system death. Initially assumed weevils but there’s not much evedence. Did have an original very compact gritty inner rootball and I potted up into looser mix….might be frost, might be over-watering…anyway. The...
Yeah I’m seeing initial “dwarf” scion needle length etc being over the top on JBP rootstock, but maybe that settles down once the root/foliage ratio evens up later on? Hard to know
Are there any clubs near you? They are the best value support you can get normally (often you can go further to other clubs as a one off to see particular demos), Bonsai Today mags and youtubers who have done apprenticeships are also a solid source of facts
You see the Bonsai Releaf guy’s latest vid features Greenwood / Corin?
He’s on facebook too - also keeping a low profile! www.facebook.com/bonsaireleaf
I’d wire them, then as soon as you can get the wire off and get them in the ground, burying the graft and wrapping wire or a tiewrap round them above the graft. You should get a fatter trunk and new roots in 1-2 years, faster in the long run than air layers/pot growing