AusBonsai

Hi everyone,
This plant was taken out of the ground last year and is throwing out great new foliage. I have been tip pruning the top to encourage more even growth.

It came from the Liverpool plains so I am assuming it is a Black Cypress Pine (Callitris endlicheri) but it could be White Cypress (Callitris glaucophylla). I am hoping someone with more knowledge could give some clarity here please.

My main reason for posting is to ask wether or not I should air layer the trunk? Upon removal it has been noted that the lower 100mm of trunck had been buried and therefore the thicker, outer bark layer has been removed. Will this grow back? If not, I would like to air layer but am not sure if the tree is a suitable candidate for this method. Any advice would be much appreciated.

With time the lower part of the trunk should bark up again, but whether or not it catches up to the upper part is hard to say. You could experiment on some sacrificial upper branches - see what happens if you damage them slightly by hitting with a pruning saw, or even rubbing with a bit of sandpaper as Aussie Bonsai Bloke does with olives. The trauma might induce some quicker and thicker bark. Or the tree may not like it and that branch could die off.

I can't say I have any experience with air layering a callitris, but you could always experiment again with growth higher up - air layer that, see how it goes.

Corky bark does grow back. It is simply the accumulation of each previous year's bark that does not shed as it ages so corky bark will continue to develop as long as the tree grows.
I had a similar problem with corky bark Chinese elms. The best solution was to rub off the corky bark above the narrow section. I know that goes against everything we are told but it does work. Removing the higher cork will restore the natural trunk taper. New corky bark will accumulate every year and in 3 years you will wonder what all the fuss was about.

Hi Dibbo ,i have several for over ten years and they are just starting to catch up ,in regards to the barking up of the lower section . They usually get a lot of moss build up during winter and come late spring i clean them up with an old toothbrush and water .I guess i was inadvertently smoothing out the transition area. I would give Shibuis suggestion a go ,actually might try this on one of mine. The foliage on yours looks like it has a blue tinge ,have found them to be a much better species to work with than those with the light green foliage (very coarse ).
Cheers John.