Two different people described it on that other thread Doug, go back and read it again or study the sources where they obtained their information. I don't think there is any sensible argument that disagrees with "healing" as a euphemism or as an acceptable approximation for general consumption but it does not appear to be acceptable currently amongst the arboriculture community. I doubt that many would agree with "close up and seal" as a convincing description of 'healing' either.
A more important statement, and one worth challenging as edzard did is that maples can bleed to death, sure "bleed" (although not blood for the really thick) is what they do, but not to the point of dying.

Trees compartmentalize disease and injury.

I've discussed this with Doug in the past and he certainly agrees with Dr. Shigo. So is it Doug that's really in there stirring it up for entertainment or is it really Pat with little knowledge ???

Gerald

Here is a link that might be useful: shigo

"Heal" is not a bad term ... when we prune a tree we "wound " the tree .. if the tree closes the wound and obstructs the invasion of pathogens or other organisms located outside the tree from getting inside .. the tree has "healed" or simply closed it's wounds. "Healing" in this sense describes the function of "healing" NOT the process or method of healing.

What arborist agree on is that unlike human wounds tree wounds rarely if ever need our assistance in healing other then not wounding the tree in the first place ( like mower and construction damage ) and making a correct pruning cut that lends itself to closing quickly and completely.

It's not that much different then your gums closing up after a tooth is pulled or when your skin is cut open it must be closed.

I don't think the late Shigo would have a problem with this term being used in this sense and I bring this thread back from the dead since Shigo's books would be a good addition for any gardener working with trees.

Good Day ...

The key point is that the tree does not return to its original condition where the branch was lost. A cavity forms that is covered over on the outside and compartmentalized on the inside, but there is still a wound left that does not go completely away. That is how it differs from healing. Some cavities may continue to be attacked by fungi for years.

Yes .. this is true .. on a process level there are differences but still wound closure can be very complete leaving only a relatively minute "scar" and along with included branch wood below the surface still sound and intact.

Cavities are not the norm but the result of poorly planned wounds or inadvertant wounding encountered as the tree grows under less then ideal conditions. Ofcourse nothing is 100 % ... but trees move slowly.

As a japanese gardener who wishes to manipulate trees it would seem to be of benafit to understand how to work with the trees system ... in some respects Shigo was a bit "rigid" in his tree work .. his original goal was working with trees for lumber straight trees with little defects .. many arborist I work with are also rigid. There is a trend against manipulating plant materials as if it can't be done in a sound manner.

Topping we all know is bad for a tree but some have suggested pollarding as not good for a tree .. one arborist well respected locally used to point out the difference between topping and well planned pollarding .. a pruning art he called it .. but later perhaps under pressure from the days dogma .. has avoided mentioning pollarding at all .. kinda a taboo subject in a crowd of arborist these days.

Can we manipulate plant materials and still have a sound tree given we understand the trees biology /growth ect..??

To what extent ? Is a bonsai tree biologicaly stable as a "textbook" well pruned Oak ?

Are Japanese gardens biologicaly sound ?

Good Day ...

Hi all
patjonking
I don't think Edzard din't jsut say "tree do not heal" where is rest of his article ? where did you find his the article ?
Some time or offten bark is covered with new tissue and coverd dead tissue/knot remain under tree's bark. size of tree's branch, age of tree, time of pruning, and how pruned makes different.
Look like healed outside.but under the bark, it is different. I have same question as you have. What is healing means?........yama