Bonsai Heresy’s Chapter 5 and Further Thoughts on Sand
This is the first in a series of blog posts to take a chapter from Bonsai Heresy: 56 Myths Exposed Using Science and Tradition and expand on it to investigate dangling questions.
Like all chapters in Bonsai Heresy, Chapter 5 is ironically titled, though this one is the longest title in the book and is nearly a conversation: ‘When I asked if he wanted a fork, he said, “You know, sharp sand makes roots fork too'”. The chapter looks into why sharp sand, used frequently in early bonsai media, was (erroneously) thought to divide roots and create better root ramification.
Most of the chapters in Bonsai Heresy relate to older bonsai in bonsai containers, as does Chapter 5, but there is a curious side story here about the use of sand as media for cuttings.
Sand is a very popular, and effective, way to root cuttings. And yet—most interestingly—if you leave the cuttings in that sand, after a month or so they are soon way behind the cuttings in other media like perlite, pumice, peat and the like.
Why is that?
Sand, especially fine sand, does provide a lot of water to the base of the cutting, which initially it needs in high quantities, being bereft of roots. Capillarity between fine sand particles keeps the cutting going, and they root well in sand.
But the other more porous media listed above do a better job of providing the other two things roots want: oxygen and nutrients, and which plants trying to power biomass production—stems, leaves, and bigger roots—also need. And this is the reason the cutting in sand begins to lag behind other media after roots have come out. And thus the cutting needs a speedy repot to different media to continue the growth momentum of the young plant.
Which, in a roundabout way, explains why other media tend to support mature tree growth better than sand does.
(Thanks to Gary Wood, one of my content editors for Bonsai Heresy, for contributing to and double-checking this blog post)