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"And the LORD God made ... trees that were pleasing to the eye ..." Gen. 2:9, New International Version.

"Bonsai isn't just something I do; it's part of what I am." Remark to my wife and daughter.

Sunday, December 19, 2021

NOT Stronger at the Broken Place

(Members of the Ft. Wayne Bonsai Club will have seen this material already, with some different wording, in a recent "Stuff from Steve".)

 Stronger at the broken place. Have you heard that expression?

It comes from the world of medicine, and has to do with the healing of a broken bone. If the broken ends of a bone are close enough to each other and the bone is otherwise healthy, those broken ends will begin to knit together. New connective tissue is laid down between them and then impregnated with calcium, becoming new bone and filling in the break.

And what often happens is that even more bone is added than was originally there. When that occurs, the result is that the healed bone becomes, literally and truly, stronger at the point where it broke than it had been before.

The expression is also used metaphorically, especially of relationships. I know very well one couple who, I am sure, would not hesitate to say that their marriage was once badly broken but is now stronger than it was before. (And their next anniversary will be their forty-fourth.)

The expression can be true of bones and marriages. But, alas, it is not true of trees.

When a woody branch or trunk breaks, the break can heal over if the broken ends are immediately aligned and immobilized, and sealed to keep out pathogens, excess moisture, and air that could cause an embolism in the water-conduction channels. But the thing to remember is that the broken wood itself will not heal. Broken living wood will never knit together as broken living bone will.

What happens is that the broken cambium and phloem layers will heal and repair themselves if given the chance. Then the cambium will start laying down new wood across the break, bridging it. Little by little that new wood will build up, thickening and strengthening the trunk or branch at that point. But underneath, the break in the wood is still there and still broken. The tree will wall off the break by chemical means so that no infections can invade the rest of the tree from it, and keep growing. But the break will always be there, down inside, and - the thing to keep in mind - as a result, a weak point will always be there.

I got an unexpected demonstration of these facts earlier this year. I did a live styling demo using a bunjin lilac at the 2018 Cherry Blossom Festival. People nearby heard the loud Crack! that announced that I had, shall we say, overestimated the flexibility of mature lilac wood. The trunk had broken more than halfway thru.

I immediately realigned the trunk to close the break, slapped on zip ties to hold it, covered the break with cut paste and vet bandage, and immobilized the trunk with sturdy wire. Here’s a picture of the repair job, taken the next spring.

The wire is supplying most of the force to keep the break closed.
The vet bandage lets the bark "breathe".

The tree leafed out and grew well the next year. In spring 2020 I removed the wire, vet bandage and zip ties. The new wood that had been laid down across the break to that point was strong enough to support the trunk. The blue ellipse marks the break site.

Spring 2020, almost two years after the break. Enough new wood has been
laid down across the break to support the trunk in normal conditions.

Close-up of the break site, spring 2020. You can see some of the swelling that
accompanies the healing-over process.

I don’t know if I forgot, or simply didn’t fully realize, that broken wood doesn’t knit and the tree was still weak at the break site. In any event, I didn’t apply any new reinforcement. That was a mistake. I discovered my error this spring, 2021, when a storm with strong winds came thru one nite. I went out the next day and found that the new wood at the break site hadn’t been strong enough to stand up to the wind. It had snapped, letting the original break in the trunk open up. By the time I found it, it had been that way for at least twelve hours. I immediately closed the break, fixed the trunk in position with a screw, and slathered cut paste liberally all around the break. But the damage was done. Within a week and a half the tree looked like this. It did not recover.

You can see the cut paste I applied after I repositioned the trunk.
Sadly, my efforts were too late.

So remember: when living wood breaks, it will not knit back together. The tree, given proper care, will bridge the break and proceed to lay down new wood across it. A time may come when enough new, healthy tissue is laid down that you will hardly be able to see that anything was ever damaged. But the tree will always be weak at the point of the break, and you will need to remember that.

:-|  :-|   :-|

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