And I would go further to add - due to the commonality of SJ juniper in landscape all over SoCal, it is pretty easy to find SJ with a 4" or greater trunk caliper. In fact, it is not uncommon for people to dig them up and throw them in the trash when remodeling.
That said, grafting juniper requires a degree of skill and sophistication, to say nothing of time commitment. Perhaps it is just me, but the majority of shimpaku I have seen at shows and exhibitions are all on their own roots. The grafted ones tend to be the exception - and are typically large trees. I know Gary Ishii has been grafting shimpaku on California juniper for years, and he has stopped doing it. Too much work and too difficult to recoup the time investment because the market for large grafted trees is a small one.
), but there's plenty of large stock that's far more developed than small cuttings. I mean - I've seen shimpaku with 4+ inch caliper trunks on them. Sure they need branch development, but they are much farther along than the smaller 5 year old cuttings you may be seeing around.
