This was my first big bonsai investment where I stopped referring to myself as a beginner bonsai artist. Purchased during a family road trip to Canberra October 2015 from Leong Kwong’s South Side Bonsai in Sydney (fig.1). It has only ever been referred to as the price I paid for it ($525), so the aptly named 525 returned to Brisbane and was left untouched for 3 months to adjust to the new climate. During that time, I pondered every aspect of this tree’s potential. When the time came to start work (six weeks later) I was surprised that wiring the first lowest branch keep me as occupied as a smaller $150 Juniper brought from Brisbane. A good month later I had completed 525’s first styling (fig.2).
In Autumn 2018, after a year and a half without unnecessary trimming, 525 was transferred into a training bonsai pot. It was in this pot that 525 was shown for the first time at the 2019 Bimer Bonsai show. During that stage my bonsai soil mix skills were at a beginner level, using general potting mix spliced with diatomite. While the soil mix had initial good drainage, 3 – 6 months later surface pooling would occur leading to a preferential drainage where sections in the root ball would likely never receive any water. I would also top up soil levels when I thought the roots were too exposed under the understanding that the nebari (root flare) grows larger when submerged in soil. This added to the conditions that led to poor drainage and water distribution, due to smaller soil particles (from the heterogeneous potting mix) settling between free pore spaces. After Winter, 525 was unresponsive to regrowth, and during Summer the foliage was showing a decline in colour and vigour. I was devastated from 525’s demise, and I have essentially done no bonsaiing since. While 525’s outcome is not ideal, it was lesson learnt – that soil mix and quality is quite possibly one of the hardest variables to keep in check with bonsai. Especially considering how harsh the Australian climate can be on a good draining soil mix with increased evaporation (and decomposition) rates.
For us as bonsai growers, soils that are fast draining will dry out quickly, and the tricks used in gardening like mulching only hinders the tiny root zone because decomposed organic matter will acts the same as small particles (yet still very important for soil health).
I 100% believe 525 died from poor drainage, due to the decomposition of organic material that lead to areas of soil compaction that resulted in other areas of preferential drainage, resulting in isolated dry zones in the root ball.
My current juniper potting mix consists of a granular 2 -5 mm mix of akadama, diatomite, pumice, and decomposed granite. I use akadama for its water holding capacity and nutrient retention, properties that are associated with clay particles. It is also a dispersive soil clay composite that breaks apart with vigorous root growth (a good thing), but leads to smaller particles that reduces pore space. As I mentioned before about Australia’s climatic conditions, dispersion is also increased by humid conditions, hence our dominant arid landscape. While the bonsai Japanese practice of repotting junipers is around 3 – 5 years, I will be repotting my plants more frequently than that. I think my mix still has a lot of room for improvement and I’d be happy to update you on further on any further revelations I have with my future bonsai soil mix.
