Air-Layering
Unique Techniques (r/bonsai)
https://www.reddit.com/r/Bonsai/s/5c8ppoFvqM
Here in socal I get roots in three months so maybe the weather has to do with it as I see way different development in the same species of trees [in the same region]; even in my garden the northern side of the air layer roots don’t grow out a much as the rest of the layer just an observation over many air layers.
Come mid February I’ll start to air layer
After scraping, I rub it down with rubbing alcohol to make sure all the live cells are destroyed.
I'll often see roots at 6 weeks but takes 4 - 5 months to get enough for separation, depending on how much sun we get.
I set them up in early june, once they have woken up proper and new growth put out.
In my climate, airlayers generally get too wet rather than too dry, so I would say make sure yours never dries out. I've had juniper airlayers staying "too wet", or so I thought, because they rooted fine.
So IPA is a sterilizing agent, which it does by dissolving the cell walls of bacteria. As far as I understand, it does basically the same thing with the cells of the cambium layer.
It's supposed to be more effective as a steriliser at 70% (rubbing alcohol) so I use that. Something to do with acting slower and penetrating deeper. It also disinfects the wound on the air layers, not of much concern for junipers but I've had agrobacterium tumesfaciens infect some air layers that are susceptible (crataegus) so it does a good job to prevent that as well.
Soak part of a cloth in it and rub down the bare wood after scraping, as well as the wound itself and the bark above it, for disinfecting. Hold it on there for a minute or so, give it a squeeze.
It dries quickly so apply hormone after. I actually rub in the powered hormone into a small bit of moist sphagnum moss, put that where it needs to go above the cut after I have mostly filled the plastic with plain sphagnum. Again, something I heard/saw online at some point.
Propagation
Advice from Idris (SBBK) for potted air-layerings—leave sphagnum on for 2 years—do not repot. Only then can remove some moss, be careful. Repot into a grow pot and not yet into a bonsai pot.