Okay I got a big ton of scoop of information that I need to type or I’ll forget some of.
65 degrees for the temperature.
bareroot perfectly fine. my friend has a channel with media in it that he sets the bareroot seedlings in and keeps that media moist.
the softer the wood (acer palmatum as an example) 14-15 days to callous
the harder the wood (beech, oak as an example) 21-22 days to callous
there’s no reason to take them out any any specific time of course. if the maples are in 18-days so be it.
he mostly hot callouses potted material but he said he also does bareroot. he knows a guy in Oregon that does strictly bareroot and this fella does Japanese maples/Acer palmatum. He callouses them and they don’t break dormancy and he then puts them in ‘something’ moist and puts them into cold storage until it’s safe planting time at which points he plants them directly into the ground.
my friend also said that early (December, January, February) the callousing bench won’t break the grafts dormancy. But he said that come March or “late” is the word I’m getting to that they certainly can. So the time you’re grafting will influence whether or not they may or may not break dormancy.
So if I was going to do this over I would use soil media to encapsulate the roots and rest the graft union only on the heating source. there’s no question ramv that the roots should be kept cool.
on a professional hot callousing bench a piece of poly is draped over it.
one last bit. the scion and union should be waxed/parafilm. and on a professional callousing bench there is a sponge that’s slightly damp (always) never soggy/ and the union is placed inside it where a slit in the sponge was made. therefore add these components to anything you do.
This is 100% the information for how to callous grafts ‘on the pipe’ as is what a hot callousing bench is called.