Does gently hitting bonsai trunks with a small hammer really increase trunk size?

Kiani

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I can't find the thread I read this in but one member wrote about it, provided a link to a source from another bonsai artist who claims it works, and explained the science behind it.

Does it really work and has an member here ever tried this method?
 

rockm

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Yeah, it works, but not in the way you really want. Swelling will occur only at the sites you hammer, which can result in lumpy looking trunks.

The steep downside is, if you don't know what you're doing, you can kill your tree pretty easily.

The results really aren't worth the effort on smaller stock. Simply allowing trees to grow results in much more attractive and convicing trunks...
 

Stan Kengai

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I have read about this technique, and from what I can recall (can't find the article, though I thought it was by Harry Harrington) it is used mainly on pines. With thinner barked species, you run the risk of crushing the soft phloem layer and causing the phloem to separate from the cambium and/or xylem. The gist of hammering is to thicken the trunk of a tree that is nearly finished/mostly developed. For less developed trees, it would be far safer to put them in the ground or to grow out sacrifice branches.

There are other artificial trunk thickening techniques for thin-barked trees, such as poking with a large needle or making small vertical incisions. These are probably a little safer than hammering, but they are still somewhat drastic measures. With these techniques, you also run the risk of infection. Again, these techniques are typically applied to nearly developed bonsai (usually in cases of reverse taper) where growing vigorously would cause a loss of fine details.
 

Vance Wood

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Do not hammer Pines, it damages the bark. Hammer deciduous trees and perforate Pines. What you are doing with these techniques is to injure the cambium and force it to heal, causing the injured area to swell. It can be a tricky technique and the results might not be as good as you might have believed it would be.
 

rockm

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The issue with doing any of this is it involves compromising the tissue that supports growth above. These techniques, as Vance says, injure an area which causes scar tissues to build up to repair the dead tissue that you've pounded/punctured/injured.

Plant scar tissue DOES NOT tranfers nutrients further up the trunk. It simply compartmentalizes the damage (fills in tissue). That means the plants ability to transfer nutrients past the damage you've caused is limited. It must find other ways around the damage. If you damage the tissue in many places all at one time, you can girdle the tree entirely, forcing it to shut down EVERYTHING above the damaged site. That means you lose the entire top of the tree...

I did this only once on an elm. The results were mostly unsightly and didn't add much. Patience and time are vastly better in producing a nice tree.
 

Ang3lfir3

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I have used the technique sparingly with a VERY sharp blade to cut slits in a tree which has a bit of wasp waste ... it helped a little however not enough that I would do it very often ..... I did it with a species that heals rather well so the scar tissue had a decent impact immediately...

not something I would suggest people run out and do ..... but a technique that when applied properly can fix an unsightly section of a tree .... in other words... understand the principles and horticulture behind it... and apply accordingly (rockm summerized the horticulture pretty well already)
 
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