It’s exploiting the natural tendency of trees to create “waterspouts” through a technique called pollarding. When a tree suffers an injury it creates a bunch of new twigs that tend to grow straight upwards if the injury is on the upper branches. The waterspouts grow more slowly and so in this species of cedar they develop those desirable properties.
This article is just a rehash or summary. Check out one of the sources it links to (since the other is broken) for details on the technique:
https://mymodernmet.com/kitayama-cedar-daisugi/
The strength & flexibility I would guess are attributable to the lack of knots and the straightness of the grain.
One thing both writers keep doing that's annoying is calling it a cedar. The tree is cryptomeria japonica, known as sugi, which in English is sometimes known by various misnomers such as "Japanese cedar" and "Japanese redwood," both of which should be taken as more poetic than scientific.
Isn't this just Pollarding and/or Coppicing, which have been practiced for at least 2000 years in Europe (and probably many other cultures as well), with a healthy dose of orientalism added on top?
“It is a little different, more like pollarding, and it doesn't work with any other conifers than saplings from one specific mutant cedar in a shrine near Kyoto.”
Are coppicing and pollarding used at all to produce timber? I had the impression that it was done only to make firewood, and was cut repeatedly without letting it grow like described in the article.
The article is pretty light on details. Essentially, the tree is first pruned to create a wide and sturdy base; once that's stable, subsequent shoots from the branches are pruned to grow vertically. The technique relies on this particular variety of cedar which tends to grow vertically but can also be made to spread out a bit. It has some advantages in space-saving and efficiency but it's also very labor-intensive.
> the lumber produced in this method is 140% as flexible as standard cedar and 200% as dense/strong,
?
The strength & flexibility I would guess are attributable to the lack of knots and the straightness of the grain.
One thing both writers keep doing that's annoying is calling it a cedar. The tree is cryptomeria japonica, known as sugi, which in English is sometimes known by various misnomers such as "Japanese cedar" and "Japanese redwood," both of which should be taken as more poetic than scientific.
Also known as 'Thing, Japan'. HN eats up articles like this every single week.
https://knowyourmeme.com/memes/thing-japan
“It is a little different, more like pollarding, and it doesn't work with any other conifers than saplings from one specific mutant cedar in a shrine near Kyoto.”
https://xcancel.com/wrathofgnon/status/1250287741247426565
https://xcancel.com/wrathofgnon/status/1250287741247426565
Some previous discussions:
2023: https://news.ycombinator.com/item?id=37759366
2021: https://news.ycombinator.com/item?id=26941631