Air Layering vs hollows, teachnical question.

[Joel]

Any horts on here? I sure hope so!

I'm not sure whereabouts to place this post, so i have made it in the "Open Table" section, even though it is bonsai related.

Hollowing a tree completely, or letting a tree rot freely is not un-heard of in bonsai. There is one particular artist, Walter Pall, who springs to mind when i think of hollowed out trees. This talented man claims that he does NOT use anything to stop the rot spreading throughout some trees such as maples. According to Mr Pall, there is not danger to the tree's health whatsoever.

According to every book Ive read on the structure of trees, and people i have talked to, the majority of the timber on the inside if the trunk is DEAD, and does not function. A small layer (underneath the cambium on most trees) called the xylem is responsible for transporting water, from the roots, to the leaves.

So, it makes sense that leaving the dead wood underneath this rot will not affect the tree, as the cambium is always dividing new cells into xylem tissue, and phloem tissue (which transports carbohydrates such as glucose around the tree).

I feel pretty much convinced that there are no issues with leaving that wood to rot (or even completely hollowing it out manually), that is until i think about air layering.

Air Layering is a technique that requires you to totally ring bark a tree to produce new roots that divide from the cambium layer. I was taught that it is safest to remove ALL tissue down to the heartwood, so that the cambium would not rejoin and supply a pathway for the sugars to get back down to the rest of the tree, thus making the tree abort any new roots stemming from the wound. The only thing joining the piece you want to layer off to the rest of the tree is the supposed "dead wood" that "does not have a function".

So why is it that you can perform an air layering on trees that you cannot strike from cutting? or branches that are too large to strike? Why can you air layer a spruce, for example, that may take two years or more for a large branch, but would never strike from cutting?

Basically, does this dead wood have any benefit to the tree or not, and if not, then why can you take an air layer on a tree that will not strike?

JayC

[Bretts]

Great question Jay.
Maybe this will answer it.
http://www.evergreengardenworks.com/airlayer.htm