Andrew Edge

Refinement is the second stage to growing a bonsai. This stage never ends and as bonsai are living and ever changing, so too refinement changes and shifts over time.

Refinement involves the build up of ramification, from primary branches, then to secondary, tertiary etc. until the fine twigs at the tips. Each of these branches becomes progressively thinner and the internodal length shorter as the branch moves away from the trunk. The fine mass of twigs at the outer silhouette is highly prized and a feature for deciduous trees when displayed in winter. Highly refined trees have a sense of age and maturity that can only be gained through years of consistent high level technique application.

The decision to put a tree into refinement is entirely up to the artist but should be a considered one. If there is a lot more girth to go on the trunk (only the artist knows when enough girth is enough) or the primary branches are still to be grown due to a trunk chop, then staying in development is the best option. But if the trunk is thick enough and the primary branches are all relatively thin then it’s time to go! For me, growing the secondaries (and so on) should be done in the bonsai pot. Growth in a developmental phase is usually quick, and growing secondaries on your branches will soon see them too thick and out of proportion to the trunk. This is wasted time and energy for you and the tree.

To get a tree into refinement, we need to first repot our trees from their plastic grow pots or boxes where they have been in development and into a bonsai pot. Large containers promote large growth so don’t choose a pot that is too much bigger than the ideal size when mature in size as a bonsai. The bonsai pot is a tool in our arsenal for controlling the vigour and energy of a tree. Subsequently we can grow the tree much more slowly and achieve a higher level of fineness to our branching. Most of the development should have been done so growth needs to be now checked and controlled.

The techniques used in refinement differ species to species and this is where understanding your trees and how they grow is paramount. For most deciduous and broadleaf evergreen trees a combination of pinching, leaf trimming, wiring and clip and grow techniques will be used to build your bonsai. Conifers have more species specific techniques utilizing both pinching and pruning to redistribute energy and suppress energy.

Fertilising is another big change for your routine. Only regulated and measured amounts should be used as opposed to the copious amounts for those trees in development. This can be challenging for those of us growing trees that are half development and half refinement. Using growing techniques such as sacrifice branches to thicken or heal wounds are chosen over heavy fertilising to maintain the energy levels of the tree. Things may take a lot longer but the end result is far superior. Soil substrate choice is crucial for refining your tree. Soil that is coarse and sharp will promote a root structure full of feeder roots. Soil that is full of pine bark and loam which breaks down quickly promotes thicker more coarse root systems.

You will often hear that what is above ground is a mirror for what is underneath the soil. This couldn’t be more true than for your substrate choice. Akadama is the substrate of choice for refining your trees to a world class standard. The tubular micro structure of the fired clay allows for the fine roots to penetrate it and ‘self scale’ the particles as the roots grow by splitting them. This in turn produces finer roots and finer branching in the tree. Hard akadama will not break down through normal conditions of watering or heat in our climate and will last for years in a bonsai pot. Kanuma is used for acid loving tree such as camellia and azalea for the same effect.

The artist needs to take on a different mindset when in refinement. Too often we have a rush rush mentality where we want our tree to be ‘finished’ or mature. It is only after five or six years of grow-ing in refinement that we even start to see the results of our work. Inter-nodal length is key to refinement and if it is too long, you’ll need to start again. Hard to do on species that don’t bud back on old wood. This is where growing trees slowly is advantageous.

I’ve heard that Kokofu-ten winning deciduous trees have had upwards of twenty years of refinement techniques applied to them. Better start now!