G'Day Ray,
please forgive my Daft nature, but I'd like to get a better handle on this (rather simple) concept - tying of the cut with wire: - my understanding is that it "discourages" reconnection between the two cuts (top & bottom of the 'ring-barking') by creating a physical barrier on the hard wood. [got it!?!]
I get the thickness of the wire measurement ~ need to allow room for the new roots to grow out of the top layer. [got that, too!?!]
BUT the 'ring-barking' still allows nutrients to flow from the roots to the leaves via the [?] Cambium [?] but not in reverse (due to the cut); if then we tighten the wire too tightly, would that not crush this Cambium layer starving the leaves and killing that branch/top of the tree!?! - How do we gauge that? Or is it sufficient to get the wire to be just tight enough to lay flat against the cambium? Not to "choke" the cambium but the be just and additional barrier?
Hi Elmar,
Shibui has given you some great information. The wire is not there to prevent the
layer healing itself. The
layer is prevented from healing by two things. The distance the top and bottom cuts are apart and the removal of all the cambium.
So, what does the wire do

First, the wire is not necessary on all species of trees. This idea came about when trying to find a way to deal with trees that tend to callus rather than develop roots. Have a look at the photo below. If you have a close look at where the red arrows are indicating, you will see the beginning of callusing but roots have also developed.
Callus.jpg
You will notice that the callus has hit the wire and not folded down. In conjunction with this I believe the callus is irritated by the wire helping it to shoot roots.
Regards Ray
You do not have the required permissions to view the files attached to this post.