AusBonsai

Hi all

I was wondering if there are any techneques on how the cut base stub is treated on air layers. I know it is shortned next repot after removal but should it be hollowed out to promote callousing .? I would imagine this would be hard to do without damaging roots.

Or do people just leave a small stub and not worry about it.

I just worried about the stub potentially rotting up through the trunk especially on trees like privet.

I just shorten the stub back to where the roots come from and leave the tree to heal over it. Doesn't take very long for the callus to grow over the cut because its always moist. If you are worried about the exposed wood rotting you can seal the cut with wound sealer just like pruning cuts above ground.
No need to hollow out the cut because no one will see it. Carving a pruning cut a bit hollow is only cosmetic - the hollow allows the thicker callus to grow over the cut without leaving an ugly lump.